# Release Notes

The CHANGELOG for the current development version is available at https://github.com/rasbt/mlxtend/blob/master/docs/sources/CHANGELOG.md.

### Version 0.17.2 (02-24-2020)

##### Downloads

##### New Features

- -

##### Changes

- The previously deprecated
`OnehotTransactions`

has been removed in favor of the`TransactionEncoder.`

- Removed
`SparseDataFrame`

support in frequent pattern mining functions in favor of pandas >=1.0's new way for working sparse data. If you used`SparseDataFrame`

formats, please see pandas' migration guide at https://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating (#667)

##### Bug Fixes

- -

### Version 0.17.1 (2020-01-28)

##### Downloads

##### New Features

- The
`SequentialFeatureSelector`

now supports using pre-specified feature sets via the`fixed_features`

parameter. (#578) - Adds a new
`accuracy_score`

function to`mlxtend.evaluate`

for computing basic classifcation accuracy, per-class accuracy, and average per-class accuracy. (#624 via Deepan Das) `StackingClassifier`

and`StackingCVClassifier`

now have a`decision_function`

method, which serves as a preferred choice over`predict_proba`

in calculating roc_auc and average_precision scores when the meta estimator is a linear model or support vector classifier. (#634 via Qiang Gu)

##### Changes

- Improve the runtime performance for the
`apriori`

frequent itemset generating function when`low_memory=True`

. Setting`low_memory=False`

(default) is still faster for small itemsets, but`low_memory=True`

can be much faster for large itemsets and requires less memory. Also, input validation for`apriori`

, ̀ fpgrowth`and`

fpmax`takes a significant amount of time when input pandas DataFrame is large; this is now dramatically reduced when input contains boolean values (and not zeros/ones), which is the case when using`

TransactionEncoder`. (#619 via Denis Barbier) - Add support for newer sparse pandas DataFrame for frequent itemset algorithms. Also, input validation for
`apriori`

, ̀ fpgrowth`and`

fpmax` runs much faster on sparse DataFrame when input pandas DataFrame contains integer values. (#621 via Denis Barbier) - Let
`fpgrowth`

and`fpmax`

directly work on sparse DataFrame, they were previously converted into dense Numpy arrays. (#622 via Denis Barbier)

##### Bug Fixes

- Fixes a bug in
`mlxtend.plotting.plot_pca_correlation_graph`

that caused the explaind variances not summing up to 1. Also, improves the runtime performance of the correlation computation and adds a missing function argument for the explained variances (eigenvalues) if users provide their own principal components. (#593 via Gabriel Azevedo Ferreira) - Behavior of
`fpgrowth`

and`apriori`

consistent for edgecases such as`min_support=0`

. (#573 via Steve Harenberg) `fpmax`

returns an empty data frame now instead of raising an error if the frequent itemset set is empty. (#573 via Steve Harenberg)- Fixes and issue in
`mlxtend.plotting.plot_confusion_matrix`

, where the font-color choice for medium-dark cells was not ideal and hard to read. #588 via sohrabtowfighi) - The
`svd`

mode of`mlxtend.feature_extraction.PrincipalComponentAnalysis`

now also*n-1*degrees of freedom instead of*n*d.o.f. when computing the eigenvalues to match the behavior of`eigen`

. #595 - Disable input validation for
`StackingCVClassifier`

because it causes issues if pipelines are used as input. #606

### Version 0.17.0 (07/19/2019)

##### Downloads

##### New Features

- Added an enhancement to the existing
`iris_data()`

such that both the UCI Repository version of the Iris dataset as well as the corrected, original version of the dataset can be loaded, which has a slight difference in two data points (consistent with Fisher's paper; this is also the same as in R). (via #539 via janismdhanbad) - Added optional
`groups`

parameter to`SequentialFeatureSelector`

and`ExhaustiveFeatureSelector`

`fit()`

methods for forwarding to sklearn CV (#537 via arc12) - Added a new
`plot_pca_correlation_graph`

function to the`mlxtend.plotting`

submodule for plotting a PCA correlation graph. (#544 via Gabriel-Azevedo-Ferreira) - Added a
`zoom_factor`

parameter to the`mlxten.plotting.plot_decision_region`

function that allows users to zoom in and out of the decision region plots. (#545) - Added a function
`fpgrowth`

that implements the FP-Growth algorithm for mining frequent itemsets as a drop-in replacement for the existing`apriori`

algorithm. (#550 via Steve Harenberg) - New
`heatmap`

function in`mlxtend.plotting`

. (#552) - Added a function
`fpmax`

that implements the FP-Max algorithm for mining maximal itemsets as a drop-in replacement for the`fpgrowth`

algorithm. (#553 via Steve Harenberg) - New
`figsize`

parameter for the`plot_decision_regions`

function in`mlxtend.plotting`

. (#555 via Mirza Hasanbasic) - New
`low_memory`

option for the`apriori`

frequent itemset generating function. Setting`low_memory=False`

(default) uses a substantially optimized version of the algorithm that is 3-6x faster than the original implementation (`low_memory=True`

). (#567 via jmayse) - Added numerically stable OLS methods which uses
`QR decomposition`

and`Singular Value Decomposition`

(SVD) methods to`LinearRegression`

in`mlxtend.regressor.linear_regression`

. (#575 via PuneetGrov3r)

##### Changes

- Now uses the latest joblib library under the hood for multiprocessing instead of
`sklearn.externals.joblib`

. (#547) - Changes to
`StackingCVClassifier`

and`StackingCVRegressor`

such that first-level models are allowed to generate output of non-numeric type. (#562)

##### Bug Fixes

- Fixed documentation of
`iris_data()`

under`iris.py`

by adding a note about differences in the iris data in R and UCI machine learning repo. - Make sure that if the
`'svd'`

mode is used in PCA, the number of eigenvalues is the same as when using`'eigen'`

(append 0's zeros in that case) (#565)

### Version 0.16.0 (05/12/2019)

##### Downloads

##### New Features

`StackingCVClassifier`

and`StackingCVRegressor`

now support`random_state`

parameter, which, together with`shuffle`

, controls the randomness in the cv splitting. (#523 via Qiang Gu)`StackingCVClassifier`

and`StackingCVRegressor`

now have a new`drop_last_proba`

parameter. It drops the last "probability" column in the feature set since if`True`

, because it is redundant: p(y_c) = 1 - p(y_1) + p(y_2) + ... + p(y_{c-1}). This can be useful for meta-classifiers that are sensitive to perfectly collinear features. (#532)- Other stacking estimators, including
`StackingClassifier`

,`StackingCVClassifier`

and`StackingRegressor`

, support grid search over the`regressors`

and even a single base regressor. (#522 via Qiang Gu) - Adds multiprocessing support to
`StackingCVClassifier`

. (#522 via Qiang Gu) - Adds multiprocessing support to
`StackingCVRegressor`

. (#512 via Qiang Gu) - Now, the
`StackingCVRegressor`

also enables grid search over the`regressors`

and even a single base regressor. When there are level-mixed parameters,`GridSearchCV`

will try to replace hyperparameters in a top-down order (see the documentation for examples details). (#515 via Qiang Gu) - Adds a
`verbose`

parameter to`apriori`

to show the current iteration number as well as the itemset size currently being sampled. (#519 - Adds an optional
`class_name`

parameter to the confusion matrix function to display class names on the axis as tick marks. (#487 via sandpiturtle) - Adds a
`pca.e_vals_normalized_`

attribute to PCA for storing the eigenvalues also in normalized form; this is commonly referred to as variance explained ratios. #545

##### Changes

- Due to new features, restructuring, and better scikit-learn support (for
`GridSearchCV`

, etc.) the`StackingCVRegressor`

's meta regressor is now being accessed via`'meta_regressor__*`

in the parameter grid. E.g., if a`RandomForestRegressor`

as meta- egressor was previously tuned via`'randomforestregressor__n_estimators'`

, this has now changed to`'meta_regressor__n_estimators'`

. (#515 via Qiang Gu) - The same change mentioned above is now applied to other stacking estimators, including
`StackingClassifier`

,`StackingCVClassifier`

and`StackingRegressor`

. (#522 via Qiang Gu) - Automatically performs mean centering for PCA solver 'SVD' such that using SVD is always equal to using the covariance matrix approach #545

##### Bug Fixes

- The
`feature_selection.ColumnSelector`

now also supports column names of type`int`

(in addition to`str`

names) if the input is a pandas DataFrame. (#500 via tetrar124 - Fix unreadable labels in
`plot_confusion_matrix`

for imbalanced datasets if`show_absolute=True`

and`show_normed=True`

. (#504) - Raises a more informative error if a
`SparseDataFrame`

is passed to`apriori`

and the dataframe has integer column names that don't start with`0`

due to current limitations of the`SparseDataFrame`

implementation in pandas. (#503) - SequentialFeatureSelector now supports DataFrame as input for all operating modes (forward/backward/floating). #506
`mlxtend.evaluate.feature_importance_permutation`

now correctly accepts scoring functions with proper function signature as`metric`

argument. #528

### Version 0.15.0 (01-19-2019)

##### Downloads

##### New Features

- Adds a new transformer class to
`mlxtend.image`

,`EyepadAlign`

, that aligns face images based on the location of the eyes. (#466 by Vahid Mirjalili) - Adds a new function,
`mlxtend.evaluate.bias_variance_decomp`

that decomposes the loss of a regressor or classifier into bias and variance terms. (#470) - Adds a
`whitening`

parameter to`PrincipalComponentAnalysis`

, to optionally whiten the transformed data such that the features have unit variance. (#475)

##### Changes

- Changed the default solver in
`PrincipalComponentAnalysis`

to`'svd'`

instead of`'eigen'`

to improve numerical stability. (#474) - The
`mlxtend.image.extract_face_landmarks`

now returns`None`

if no facial landmarks were detected instead of an array of all zeros. (#466)

##### Bug Fixes

- The eigenvectors maybe have not been sorted in certain edge cases if solver was
`'eigen'`

in`PrincipalComponentAnalysis`

and`LinearDiscriminantAnalysis`

. (#477, #478)

### Version 0.14.0 (11-09-2018)

##### Downloads

##### New Features

- Added a
`scatterplotmatrix`

function to the`plotting`

module. (#437) - Added
`sample_weight`

option to`StackingRegressor`

,`StackingClassifier`

,`StackingCVRegressor`

,`StackingCVClassifier`

,`EnsembleVoteClassifier`

. (#438) - Added a
`RandomHoldoutSplit`

class to perform a random train/valid split without rotation in`SequentialFeatureSelector`

, scikit-learn`GridSearchCV`

etc. (#442) - Added a
`PredefinedHoldoutSplit`

class to perform a train/valid split, based on user-specified indices, without rotation in`SequentialFeatureSelector`

, scikit-learn`GridSearchCV`

etc. (#443) - Created a new
`mlxtend.image`

submodule for working on image processing-related tasks. (#457) - Added a new convenience function
`extract_face_landmarks`

based on`dlib`

to`mlxtend.image`

. (#458) - Added a
`method='oob'`

option to the`mlxtend.evaluate.bootstrap_point632_score`

method to compute the classic out-of-bag bootstrap estimate (#459) - Added a
`method='.632+'`

option to the`mlxtend.evaluate.bootstrap_point632_score`

method to compute the .632+ bootstrap estimate that addresses the optimism bias of the .632 bootstrap (#459) - Added a new
`mlxtend.evaluate.ftest`

function to perform an F-test for comparing the accuracies of two or more classification models. (#460) - Added a new
`mlxtend.evaluate.combined_ftest_5x2cv`

function to perform an combined 5x2cv F-Test for comparing the performance of two models. (#461) - Added a new
`mlxtend.evaluate.difference_proportions`

test for comparing two proportions (e.g., classifier accuracies) (#462)

##### Changes

- Addressed deprecations warnings in NumPy 0.15. (#425)
- Because of complications in PR (#459), Python 2.7 was now dropped; since official support for Python 2.7 by the Python Software Foundation is ending in approx. 12 months anyways, this re-focussing will hopefully free up some developer time with regard to not having to worry about backward compatibility

##### Bug Fixes

- Fixed an issue with a missing import in
`mlxtend.plotting.plot_confusion_matrix`

. (#428)

### Version 0.13.0 (2018-07-20)

##### Downloads

##### New Features

- A meaningful error message is now raised when a cross-validation generator is used with
`SequentialFeatureSelector`

. (#377) - The
`SequentialFeatureSelector`

now accepts custom feature names via the`fit`

method for more interpretable feature subset reports. (#379) - The
`SequentialFeatureSelector`

is now also compatible with Pandas DataFrames and uses DataFrame column-names for more interpretable feature subset reports. (#379) `ColumnSelector`

now works with Pandas DataFrames columns. (#378 by Manuel Garrido)- The
`ExhaustiveFeatureSelector`

estimator in`mlxtend.feature_selection`

now is safely stoppable mid-process by control+c. (#380) - Two new functions,
`vectorspace_orthonormalization`

and`vectorspace_dimensionality`

were added to`mlxtend.math`

to use the Gram-Schmidt process to convert a set of linearly independent vectors into a set of orthonormal basis vectors, and to compute the dimensionality of a vectorspace, respectively. (#382) `mlxtend.frequent_patterns.apriori`

now supports pandas`SparseDataFrame`

s to generate frequent itemsets. (#404 via Daniel Morales)- The
`plot_confusion_matrix`

function now has the ability to show normalized confusion matrix coefficients in addition to or instead of absolute confusion matrix coefficients with or without a colorbar. The text display method has been changed so that the full range of the colormap is used. The default size is also now set based on the number of classes. - Added support for merging the meta features with the original input features in
`StackingRegressor`

(via`use_features_in_secondary`

) like it is already supported in the other Stacking classes. (#418) - Added a
`support_only`

to the`association_rules`

function, which allow constructing association rules (based on the support metric only) for cropped input DataFrames that don't contain a complete set of antecedent and consequent support values. (#421)

##### Changes

- Itemsets generated with
`apriori`

are now`frozenset`

s (#393 by William Laney and #394) - Now raises an error if a input DataFrame to
`apriori`

contains non 0, 1, True, False values. #419)

##### Bug Fixes

- Allow mlxtend estimators to be cloned via scikit-learn's
`clone`

function. (#374) - Fixes bug to allow the correct use of
`refit=False`

in`StackingRegressor`

and`StackingCVRegressor`

(#384 and (#385) by selay01) - Allow
`StackingClassifier`

to work with sparse matrices when`use_features_in_secondary=True`

(#408 by Floris Hoogenbook) - Allow
`StackingCVRegressor`

to work with sparse matrices when`use_features_in_secondary=True`

(#416) - Allow
`StackingCVClassifier`

to work with sparse matrices when`use_features_in_secondary=True`

(#417)

### Version 0.12.0 (2018-21-04)

##### Downloads

##### New Features

- A new
`feature_importance_permuation`

function to compute the feature importance in classifiers and regressors via the*permutation importance*method (#358) - The fit method of the
`ExhaustiveFeatureSelector`

now optionally accepts`**fit_params`

for the estimator that is used for the feature selection. (#354 by Zach Griffith) - The fit method of the
`SequentialFeatureSelector`

now optionally accepts`**fit_params`

for the estimator that is used for the feature selection. (#350 by Zach Griffith)

##### Changes

- Replaced
`plot_decision_regions`

colors by a colorblind-friendly palette and adds contour lines for decision regions. (#348) - All stacking estimators now raise
`NonFittedErrors`

if any method for inference is called prior to fitting the estimator. (#353) - Renamed the
`refit`

parameter of both the`StackingClassifier`

and`StackingCVClassifier`

to`use_clones`

to be more explicit and less misleading. (#368)

##### Bug Fixes

- Various changes in the documentation and documentation tools to fix formatting issues (#363)
- Fixes a bug where the
`StackingCVClassifier`

's meta features were not stored in the original order when`shuffle=True`

(#370) - Many documentation improvements, including links to the User Guides in the API docs (#371)

### Version 0.11.0 (2018-03-14)

##### Downloads

##### New Features

- New function implementing the resampled paired t-test procedure (
`paired_ttest_resampled`

) to compare the performance of two models. (#323) - New function implementing the k-fold paired t-test procedure (
`paired_ttest_kfold_cv`

) to compare the performance of two models (also called k-hold-out paired t-test). (#324) - New function implementing the 5x2cv paired t-test procedure (
`paired_ttest_5x2cv`

) proposed by Dieterrich (1998) to compare the performance of two models. (#325) - A
`refit`

parameter was added to stacking classes (similar to the`refit`

parameter in the`EnsembleVoteClassifier`

), to support classifiers and regressors that follow the scikit-learn API but are not compatible with scikit-learn's`clone`

function. (#322) - The
`ColumnSelector`

now has a`drop_axis`

argument to use it in pipelines with`CountVectorizers`

. (#333)

##### Changes

- Raises an informative error message if
`predict`

or`predict_meta_features`

is called prior to calling the`fit`

method in`StackingRegressor`

and`StackingCVRegressor`

. (#315) - The
`plot_decision_regions`

function now automatically determines the optimal setting based on the feature dimensions and supports anti-aliasing. The old`res`

parameter has been deprecated. (#309 by Guillaume Poirier-Morency) - Apriori code is faster due to optimization in
`onehot transformation`

and the amount of candidates generated by the`apriori`

algorithm. (#327 by Jakub Smid) - The
`OnehotTransactions`

class (which is typically often used in combination with the`apriori`

function for association rule mining) is now more memory efficient as it uses boolean arrays instead of integer arrays. In addition, the`OnehotTransactions`

class can be now be provided with`sparse`

argument to generate sparse representations of the`onehot`

matrix to further improve memory efficiency. (#328 by Jakub Smid) - The
`OneHotTransactions`

has been deprecated and replaced by the`TransactionEncoder`

. (#332 - The
`plot_decision_regions`

function now has three new parameters,`scatter_kwargs`

,`contourf_kwargs`

, and`scatter_highlight_kwargs`

, that can be used to modify the plotting style. (#342 by James Bourbeau)

##### Bug Fixes

- Fixed issue when class labels were provided to the
`EnsembleVoteClassifier`

when`refit`

was set to`false`

. (#322) - Allow arrays with 16-bit and 32-bit precision in
`plot_decision_regions`

function. (#337) - Fixed bug that raised an indexing error if the number of items was <= 1 when computing association rules using the conviction metric. (#340)

### Version 0.10.0 (2017-12-22)

##### Downloads

##### New Features

- New
`store_train_meta_features`

parameter for`fit`

in StackingCVRegressor. if True, train meta-features are stored in`self.train_meta_features_`

. New`pred_meta_features`

method for`StackingCVRegressor`

. People can get test meta-features using this method. (#294 via takashioya) - The new
`store_train_meta_features`

attribute and`pred_meta_features`

method for the`StackingCVRegressor`

were also added to the`StackingRegressor`

,`StackingClassifier`

, and`StackingCVClassifier`

(#299 & #300) - New function (
`evaluate.mcnemar_tables`

) for creating multiple 2x2 contigency from model predictions arrays that can be used in multiple McNemar (post-hoc) tests or Cochran's Q or F tests, etc. (#307) - New function (
`evaluate.cochrans_q`

) for performing Cochran's Q test to compare the accuracy of multiple classifiers. (#310)

##### Changes

- Added
`requirements.txt`

to`setup.py`

. (#304 via Colin Carrol)

##### Bug Fixes

- Improved numerical stability for p-values computed via the the exact McNemar test (#306)
`nose`

is not required to use the library (#302)

### Version 0.9.1 (2017-11-19)

##### Downloads

##### New Features

- Added
`mlxtend.evaluate.bootstrap_point632_score`

to evaluate the performance of estimators using the .632 bootstrap. (#283) - New
`max_len`

parameter for the frequent itemset generation via the`apriori`

function to allow for early stopping. (#270)

##### Changes

- All feature index tuples in
`SequentialFeatureSelector`

or now in sorted order. (#262) - The
`SequentialFeatureSelector`

now runs the continuation of the floating inclusion/exclusion as described in Novovicova & Kittler (1994). Note that this didn't cause any difference in performance on any of the test scenarios but could lead to better performance in certain edge cases. (#262) `utils.Counter`

now accepts a name variable to help distinguish between multiple counters, time precision can be set with the 'precision' kwarg and the new attribute end_time holds the time the last iteration completed. (#278 via Mathew Savage)

##### Bug Fixes

- Fixed an deprecation error that occured with McNemar test when using SciPy 1.0. (#283)

### Version 0.9.0 (2017-10-21)

##### Downloads

##### New Features

- Added
`evaluate.permutation_test`

, a permutation test for hypothesis testing (or A/B testing) to test if two samples come from the same distribution. Or in other words, a procedure to test the null hypothesis that that two groups are not significantly different (e.g., a treatment and a control group). (#250) - Added
`'leverage'`

and`'conviction`

as evaluation metrics to the`frequent_patterns.association_rules`

function. (#246 & #247) - Added a
`loadings_`

attribute to`PrincipalComponentAnalysis`

to compute the factor loadings of the features on the principal components. (#251) - Allow grid search over classifiers/regressors in ensemble and stacking estimators. (#259)
- New
`make_multiplexer_dataset`

function that creates a dataset generated by a n-bit Boolean multiplexer for evaluating supervised learning algorithms. (#263) - Added a new
`BootstrapOutOfBag`

class, an implementation of the out-of-bag bootstrap to evaluate supervised learning algorithms. (#265) - The parameters for
`StackingClassifier`

,`StackingCVClassifier`

,`StackingRegressor`

,`StackingCVRegressor`

, and`EnsembleVoteClassifier`

can now be tuned using scikit-learn's`GridSearchCV`

(#254 via James Bourbeau)

##### Changes

- The
`'support'`

column returned by`frequent_patterns.association_rules`

was changed to compute the support of "antecedant union consequent", and new`antecedant support'`

and`'consequent support'`

column were added to avoid ambiguity. (#245) - Allow the
`OnehotTransactions`

to be cloned via scikit-learn's`clone`

function, which is required by e.g., scikit-learn's`FeatureUnion`

or`GridSearchCV`

(via Iaroslav Shcherbatyi). (#249)

##### Bug Fixes

- Fix issues with
`self._init_time`

parameter in`_IterativeModel`

subclasses. (#256) - Fix imprecision bug that occurred in
`plot_ecdf`

when run on Python 2.7. (264) - The vectors from SVD in
`PrincipalComponentAnalysis`

are now being scaled so that the eigenvalues via`solver='eigen'`

and`solver='svd'`

now store eigenvalues that have the same magnitudes. (#251)

### Version 0.8.0 (2017-09-09)

##### Downloads

##### New Features

- Added a
`mlxtend.evaluate.bootstrap`

that implements the ordinary nonparametric bootstrap to bootstrap a single statistic (for example, the mean. median, R^2 of a regression fit, and so forth) #232 `SequentialFeatureSelecor`

's`k_features`

now accepts a string argument "best" or "parsimonious" for more "automated" feature selection. For instance, if "best" is provided, the feature selector will return the feature subset with the best cross-validation performance. If "parsimonious" is provided as an argument, the smallest feature subset that is within one standard error of the cross-validation performance will be selected. #238

##### Changes

`SequentialFeatureSelector`

now uses`np.nanmean`

over normal mean to support scorers that may return`np.nan`

#211 (via mrkaiser)- The
`skip_if_stuck`

parameter was removed from`SequentialFeatureSelector`

in favor of a more efficient implementation comparing the conditional inclusion/exclusion results (in the floating versions) to the performances of previously sampled feature sets that were cached #237 `ExhaustiveFeatureSelector`

was modified to consume substantially less memory #195 (via Adam Erickson)

##### Bug Fixes

- Fixed a bug where the
`SequentialFeatureSelector`

selected a feature subset larger than then specified via the`k_features`

tuple max-value #213

### Version 0.7.0 (2017-06-22)

##### Downloads

##### New Features

- New mlxtend.plotting.ecdf function for plotting empirical cumulative distribution functions (#196).
- New
`StackingCVRegressor`

for stacking regressors with out-of-fold predictions to prevent overfitting (#201via Eike Dehling).

##### Changes

- The TensorFlow estimator have been removed from mlxtend, since TensorFlow has now very convenient ways to build on estimators, which render those implementations obsolete.
`plot_decision_regions`

now supports plotting decision regions for more than 2 training features #189, via James Bourbeau).- Parallel execution in
`mlxtend.feature_selection.SequentialFeatureSelector`

and`mlxtend.feature_selection.ExhaustiveFeatureSelector`

is now performed over different feature subsets instead of the different cross-validation folds to better utilize machines with multiple processors if the number of features is large (#193, via @whalebot-helmsman). - Raise meaningful error messages if pandas
`DataFrame`

s or Python lists of lists are fed into the`StackingCVClassifer`

as a`fit`

arguments (198). - The
`n_folds`

parameter of the`StackingCVClassifier`

was changed to`cv`

and can now accept any kind of cross validation technique that is available from scikit-learn. For example,`StackingCVClassifier(..., cv=StratifiedKFold(n_splits=3))`

or`StackingCVClassifier(..., cv=GroupKFold(n_splits=3))`

(#203, via Konstantinos Paliouras).

##### Bug Fixes

`SequentialFeatureSelector`

now correctly accepts a`None`

argument for the`scoring`

parameter to infer the default scoring metric from scikit-learn classifiers and regressors (#171).- The
`plot_decision_regions`

function now supports pre-existing axes objects generated via matplotlib's`plt.subplots`

. (#184, see example) - Made
`math.num_combinations`

and`math.num_permutations`

numerically stable for large numbers of combinations and permutations (#200).

### Version 0.6.0 (2017-03-18)

##### Downloads

##### New Features

- An
`association_rules`

function is implemented that allows to generate rules based on a list of frequent itemsets (via Joshua Goerner).

##### Changes

- Adds a black
`edgecolor`

to plots via`plotting.plot_decision_regions`

to make markers more distinguishable from the background in`matplotlib>=2.0`

. - The
`association`

submodule was renamed to`frequent_patterns`

.

##### Bug Fixes

- The
`DataFrame`

index of`apriori`

results are now unique and ordered. - Fixed typos in autompg and wine datasets (via James Bourbeau).

### Version 0.5.1 (2017-02-14)

##### Downloads

##### New Features

- The
`EnsembleVoteClassifier`

has a new`refit`

attribute that prevents refitting classifiers if`refit=False`

to save computational time. - Added a new
`lift_score`

function in`evaluate`

to compute lift score (via Batuhan Bardak). `StackingClassifier`

and`StackingRegressor`

support multivariate targets if the underlying models do (via kernc).`StackingClassifier`

has a new`use_features_in_secondary`

attribute like`StackingCVClassifier`

.

##### Changes

- Changed default verbosity level in
`SequentialFeatureSelector`

to 0 - The
`EnsembleVoteClassifier`

now raises a`NotFittedError`

if the estimator wasn't`fit`

before calling`predict`

. (via Anton Loss) - Added new TensorFlow variable initialization syntax to guarantee compatibility with TensorFlow 1.0

##### Bug Fixes

- Fixed wrong default value for
`k_features`

in`SequentialFeatureSelector`

- Cast selected feature subsets in the
`SequentialFeautureSelector`

as sets to prevent the iterator from getting stuck if the`k_idx`

are different permutations of the same combination (via Zac Wellmer). - Fixed an issue with learning curves that caused the performance metrics to be reversed (via ipashchenko)
- Fixed a bug that could occur in the
`SequentialFeatureSelector`

if there are similarly-well performing subsets in the floating variants (via Zac Wellmer).

### Version 0.5.0 (2016-11-09)

##### Downloads

##### New Features

- New
`ExhaustiveFeatureSelector`

estimator in`mlxtend.feature_selection`

for evaluating all feature combinations in a specified range - The
`StackingClassifier`

has a new parameter`average_probas`

that is set to`True`

by default to maintain the current behavior. A deprecation warning was added though, and it will default to`False`

in future releases (0.6.0);`average_probas=False`

will result in stacking of the level-1 predicted probabilities rather than averaging these. - New
`StackingCVClassifier`

estimator in 'mlxtend.classifier' for implementing a stacking ensemble that uses cross-validation techniques for training the meta-estimator to avoid overfitting (Reiichiro Nakano) - New
`OnehotTransactions`

encoder class added to the`preprocessing`

submodule for transforming transaction data into a one-hot encoded array - The
`SequentialFeatureSelector`

estimator in`mlxtend.feature_selection`

now is safely stoppable mid-process by control+c, and deprecated`print_progress`

in favor of a more tunable`verbose`

parameter (Will McGinnis) - New
`apriori`

function in`association`

to extract frequent itemsets from transaction data for association rule mining - New
`checkerboard_plot`

function in`plotting`

to plot checkerboard tables / heat maps - New
`mcnemar_table`

and`mcnemar`

functions in`evaluate`

to compute 2x2 contingency tables and McNemar's test

##### Changes

- All plotting functions have been moved to
`mlxtend.plotting`

for compatibility reasons with continuous integration services and to make the installation of`matplotlib`

optional for users of`mlxtend`

's core functionality - Added a compatibility layer for
`scikit-learn 0.18`

using the new`model_selection`

module while maintaining backwards compatibility to scikit-learn 0.17.

##### Bug Fixes

`mlxtend.plotting.plot_decision_regions`

now draws decision regions correctly if more than 4 class labels are present- Raise
`AttributeError`

in`plot_decision_regions`

when the`X_higlight`

argument is a 1D array (chkoar)

### Version 0.4.2 (2016-08-24)

##### Downloads

##### New Features

- Added
`preprocessing.CopyTransformer`

, a mock class that returns copies of imput arrays via`transform`

and`fit_transform`

##### Changes

- Added AppVeyor to CI to ensure MS Windows compatibility
- Dataset are now saved as compressed .txt or .csv files rather than being imported as Python objects
`feature_selection.SequentialFeatureSelector`

now supports the selection of`k_features`

using a tuple to specify a "min-max"`k_features`

range- Added "SVD solver" option to the
`PrincipalComponentAnalysis`

- Raise a
`AttributeError`

with "not fitted" message in`SequentialFeatureSelector`

if`transform`

or`get_metric_dict`

are called prior to`fit`

- Use small, positive bias units in
`TfMultiLayerPerceptron`

's hidden layer(s) if the activations are ReLUs in order to avoid dead neurons - Added an optional
`clone_estimator`

parameter to the`SequentialFeatureSelector`

that defaults to`True`

, avoiding the modification of the original estimator objects - More rigorous type and shape checks in the
`evaluate.plot_decision_regions`

function `DenseTransformer`

now doesn't raise and error if the input array is*not*sparse- API clean-up using scikit-learn's
`BaseEstimator`

as parent class for`feature_selection.ColumnSelector`

##### Bug Fixes

- Fixed a problem when a tuple-range was provided as argument to the
`SequentialFeatureSelector`

's`k_features`

parameter and the scoring metric was more negative than -1 (e.g., as in scikit-learn's MSE scoring function) (wahutch](https://github.com/wahutch)) - Fixed an
`AttributeError`

issue when`verbose`

> 1 in`StackingClassifier`

- Fixed a bug in
`classifier.SoftmaxRegression`

where the mean values of the offsets were used to update the bias units rather than their sum - Fixed rare bug in MLP
`_layer_mapping`

functions that caused a swap between the random number generation seed when initializing weights and biases

### Version 0.4.1 (2016-05-01)

##### Downloads

##### New Features

- New TensorFlow estimator for Linear Regression (
`tf_regressor.TfLinearRegression`

) - New k-means clustering estimator (
`cluster.Kmeans`

) - New TensorFlow k-means clustering estimator (
`tf_cluster.Kmeans`

)

##### Changes

- Due to refactoring of the estimator classes, the
`init_weights`

parameter of the`fit`

methods was globally renamed to`init_params`

- Overall performance improvements of estimators due to code clean-up and refactoring
- Added several additional checks for correct array types and more meaningful exception messages
- Added optional
`dropout`

to the`tf_classifier.TfMultiLayerPerceptron`

classifier for regularization - Added an optional
`decay`

parameter to the`tf_classifier.TfMultiLayerPerceptron`

classifier for adaptive learning via an exponential decay of the learning rate eta - Replaced old
`NeuralNetMLP`

by more streamlined`MultiLayerPerceptron`

(`classifier.MultiLayerPerceptron`

); now also with softmax in the output layer and categorical cross-entropy loss. - Unified
`init_params`

parameter for fit functions to continue training where the algorithm left off (if supported)

### Version 0.4.0 (2016-04-09)

##### New Features

- New
`TfSoftmaxRegression`

classifier using Tensorflow (`tf_classifier.TfSoftmaxRegression`

) - New
`SoftmaxRegression`

classifier (`classifier.SoftmaxRegression`

) - New
`TfMultiLayerPerceptron`

classifier using Tensorflow (`tf_classifier.TfMultiLayerPerceptron`

) - New
`StackingRegressor`

(`regressor.StackingRegressor`

) - New
`StackingClassifier`

(`classifier.StackingClassifier`

) - New function for one-hot encoding of class labels (
`preprocessing.one_hot`

) - Added
`GridSearch`

support to the`SequentialFeatureSelector`

(`feature_selection/.SequentialFeatureSelector`

) `evaluate.plot_decision_regions`

improvements:- Function now handles class y-class labels correctly if array is of type
`float`

- Correct handling of input arguments
`markers`

and`colors`

- Accept an existing
`Axes`

via the`ax`

argument

- Function now handles class y-class labels correctly if array is of type
- New
`print_progress`

parameter for all generalized models and multi-layer neural networks for printing time elapsed, ETA, and the current cost of the current epoch - Minibatch learning for
`classifier.LogisticRegression`

,`classifier.Adaline`

, and`regressor.LinearRegression`

plus streamlined API - New Principal Component Analysis class via
`mlxtend.feature_extraction.PrincipalComponentAnalysis`

- New RBF Kernel Principal Component Analysis class via
`mlxtend.feature_extraction.RBFKernelPCA`

- New Linear Discriminant Analysis class via
`mlxtend.feature_extraction.LinearDiscriminantAnalysis`

##### Changes

- The
`column`

parameter in`mlxtend.preprocessing.standardize`

now defaults to`None`

to standardize all columns more conveniently

### Version 0.3.0 (2016-01-31)

##### Downloads

##### New Features

- Added a progress bar tracker to
`classifier.NeuralNetMLP`

- Added a function to score predicted vs. target class labels
`evaluate.scoring`

- Added confusion matrix functions to create (
`evaluate.confusion_matrix`

) and plot (`evaluate.plot_confusion_matrix`

) confusion matrices - New style parameter and improved axis scaling in
`mlxtend.evaluate.plot_learning_curves`

- Added
`loadlocal_mnist`

to`mlxtend.data`

for streaming MNIST from a local byte files into numpy arrays - New
`NeuralNetMLP`

parameters:`random_weights`

,`shuffle_init`

,`shuffle_epoch`

- New
`SFS`

features such as the generation of pandas`DataFrame`

results tables and plotting functions (with confidence intervals, standard deviation, and standard error bars) - Added support for regression estimators in
`SFS`

- Added Boston
`housing dataset`

- New
`shuffle`

parameter for`classifier.NeuralNetMLP`

##### Changes

- The
`mlxtend.preprocessing.standardize`

function now optionally returns the parameters, which are estimated from the array, for re-use. A further improvement makes the`standardize`

function smarter in order to avoid zero-division errors - Cosmetic improvements to the
`evaluate.plot_decision_regions`

function such as hiding plot axes - Renaming of
`classifier.EnsembleClassfier`

to`classifier.EnsembleVoteClassifier`

- Improved random weight initialization in
`Perceptron`

,`Adaline`

,`LinearRegression`

, and`LogisticRegression`

- Changed
`learning`

parameter of`mlxtend.classifier.Adaline`

to`solver`

and added "normal equation" as closed-form solution solver - Hide y-axis labels in
`mlxtend.evaluate.plot_decision_regions`

in 1 dimensional evaluations - Sequential Feature Selection algorithms were unified into a single
`SequentialFeatureSelector`

class with parameters to enable floating selection and toggle between forward and backward selection. - Stratified sampling of MNIST (now 500x random samples from each of the 10 digit categories)
- Renaming
`mlxtend.plotting`

to`mlxtend.general_plotting`

in order to distinguish general plotting function from specialized utility function such as`evaluate.plot_decision_regions`

### Version 0.2.9 (2015-07-14)

##### Downloads

##### New Features

- Sequential Feature Selection algorithms: SFS, SFFS, SBS, and SFBS

##### Changes

- Changed
`regularization`

&`lambda`

parameters in`LogisticRegression`

to single parameter`l2_lambda`

### Version 0.2.8 (2015-06-27)

- API changes:
`mlxtend.sklearn.EnsembleClassifier`

->`mlxtend.classifier.EnsembleClassifier`

`mlxtend.sklearn.ColumnSelector`

->`mlxtend.feature_selection.ColumnSelector`

`mlxtend.sklearn.DenseTransformer`

->`mlxtend.preprocessing.DenseTransformer`

`mlxtend.pandas.standardizing`

->`mlxtend.preprocessing.standardizing`

`mlxtend.pandas.minmax_scaling`

->`mlxtend.preprocessing.minmax_scaling`

`mlxtend.matplotlib`

->`mlxtend.plotting`

- Added momentum learning parameter (alpha coefficient) to
`mlxtend.classifier.NeuralNetMLP`

. - Added adaptive learning rate (decrease constant) to
`mlxtend.classifier.NeuralNetMLP`

. `mlxtend.pandas.minmax_scaling`

became`mlxtend.preprocessing.minmax_scaling`

and also supports NumPy arrays now`mlxtend.pandas.standardizing`

became`mlxtend.preprocessing.standardizing`

and now supports both NumPy arrays and pandas DataFrames; also, now`ddof`

parameters to set the degrees of freedom when calculating the standard deviation

### Version 0.2.7 (2015-06-20)

- Added multilayer perceptron (feedforward artificial neural network) classifier as
`mlxtend.classifier.NeuralNetMLP`

. - Added 5000 labeled trainingsamples from the MNIST handwritten digits dataset to
`mlxtend.data`

### Version 0.2.6 (2015-05-08)

- Added ordinary least square regression using different solvers (gradient and stochastic gradient descent, and the closed form solution (normal equation)
- Added option for random weight initialization to logistic regression classifier and updated l2 regularization
- Added
`wine`

dataset to`mlxtend.data`

- Added
`invert_axes`

parameter`mlxtend.matplotlib.enrichtment_plot`

to optionally plot the "Count" on the x-axis - New
`verbose`

parameter for`mlxtend.sklearn.EnsembleClassifier`

by Alejandro C. Bahnsen - Added
`mlxtend.pandas.standardizing`

to standardize columns in a Pandas DataFrame - Added parameters
`linestyles`

and`markers`

to`mlxtend.matplotlib.enrichment_plot`

`mlxtend.regression.lin_regplot`

automatically adds np.newaxis and works w. python lists- Added tokenizers:
`mlxtend.text.extract_emoticons`

and`mlxtend.text.extract_words_and_emoticons`

### Version 0.2.5 (2015-04-17)

- Added Sequential Backward Selection (mlxtend.sklearn.SBS)
- Added
`X_highlight`

parameter to`mlxtend.evaluate.plot_decision_regions`

for highlighting test data points. - Added mlxtend.regression.lin_regplot to plot the fitted line from linear regression.
- Added mlxtend.matplotlib.stacked_barplot to conveniently produce stacked barplots using pandas
`DataFrame`

s. - Added mlxtend.matplotlib.enrichment_plot

### Version 0.2.4 (2015-03-15)

- Added
`scoring`

to`mlxtend.evaluate.learning_curves`

(by user pfsq) - Fixed setup.py bug caused by the missing README.html file
- matplotlib.category_scatter for pandas DataFrames and Numpy arrays

### Version 0.2.3 (2015-03-11)

- Added Logistic regression
- Gradient descent and stochastic gradient descent perceptron was changed to Adaline (Adaptive Linear Neuron)
- Perceptron and Adaline for {0, 1} classes
- Added
`mlxtend.preprocessing.shuffle_arrays_unison`

function to shuffle one or more NumPy arrays. - Added shuffle and random seed parameter to stochastic gradient descent classifier.
- Added
`rstrip`

parameter to`mlxtend.file_io.find_filegroups`

to allow trimming of base names. - Added
`ignore_substring`

parameter to`mlxtend.file_io.find_filegroups`

and`find_files`

. - Replaced .rstrip in
`mlxtend.file_io.find_filegroups`

with more robust regex. - Gridsearch support for
`mlxtend.sklearn.EnsembleClassifier`

### Version 0.2.2 (2015-03-01)

- Improved robustness of EnsembleClassifier.
- Extended plot_decision_regions() functionality for plotting 1D decision boundaries.
- Function matplotlib.plot_decision_regions was reorganized to evaluate.plot_decision_regions .
- evaluate.plot_learning_curves() function added.
- Added Rosenblatt, gradient descent, and stochastic gradient descent perceptrons.

### Version 0.2.1 (2015-01-20)

- Added mlxtend.pandas.minmax_scaling - a function to rescale pandas DataFrame columns.
- Slight update to the EnsembleClassifier interface (additional
`voting`

parameter) - Fixed EnsembleClassifier to return correct class labels if class labels are not integers from 0 to n.
- Added new matplotlib function to plot decision regions of classifiers.

### Version 0.2.0 (2015-01-13)

- Improved mlxtend.text.generalize_duplcheck to remove duplicates and prevent endless looping issue.
- Added
`recursive`

search parameter to mlxtend.file_io.find_files. - Added
`check_ext`

parameter mlxtend.file_io.find_files to search based on file extensions. - Default parameter to ignore invisible files for mlxtend.file_io.find.
- Added
`transform`

and`fit_transform`

to the`EnsembleClassifier`

. - Added mlxtend.file_io.find_filegroups function.

### Version 0.1.9 (2015-01-10)

- Implemented scikit-learn EnsembleClassifier (majority voting rule) class.

### Version 0.1.8 (2015-01-07)

- Improvements to mlxtend.text.generalize_names to handle certain Dutch last name prefixes (van, van der, de, etc.).
- Added mlxtend.text.generalize_name_duplcheck function to apply mlxtend.text.generalize_names function to a pandas DataFrame without creating duplicates.

### Version 0.1.7 (2015-01-07)

- Added text utilities with name generalization function.
- Added and file_io utilities.

### Version 0.1.6 (2015-01-04)

- Added combinations and permutations estimators.

### Version 0.1.5 (2014-12-11)

- Added
`DenseTransformer`

for pipelines and grid search.

### Version 0.1.4 (2014-08-20)

`mean_centering`

function is now a Class that creates`MeanCenterer`

objects that can be used to fit data via the`fit`

method, and center data at the column means via the`transform`

and`fit_transform`

method.

### Version 0.1.3 (2014-08-19)

- Added
`preprocessing`

module and`mean_centering`

function.

### Version 0.1.2 (2014-08-19)

- Added
`matplotlib`

utilities and`remove_borders`

function.

### Version 0.1.1 (2014-08-13)

- Simplified code for ColumnSelector.