Logistic Regression
===================

.. figure:: icons/logistic-regression.png

Logistic Regression Learner

Signals
-------

**Inputs**:

-  **Data**

   A data set

- **Preprocessor**

   Preprocessed data

**Outputs**:

-  **Learner**

   A logistic regression learning algorithm with settings as specified in
   the dialog.

-  **Logistic Regression Classifier**

   A trained classifier (a subtype of Classifier). The **Logistic Regression
   Classifier** sends data only if data input is present.

Description
-----------

.. figure:: images/LogisticRegression-stamped.png

1. A name under which the learner appears in other widgets. The default
   name is "Logistic Regression".
2. `Regularization <https://en.wikipedia.org/wiki/Regularization_(mathematics)>`_
   type (either
   `L1 <https://en.wikipedia.org/wiki/Least_squares#Lasso_method>`_ or
   `L2 <https://en.wikipedia.org/wiki/Tikhonov_regularization>`_). Set
   the cost strength (default is C=1).
3. Press *Apply* to commit changes. If *Apply Automatically* is ticked, changes will be communicated automatically. 

Example
-------

The widget is used just as any other widget for inducing a classifier. This is an example demonstrating the prediction value of logistic regression used on the *voting.tab* data set. We first use the **Logistic Regression** learner to provide a LR classifier for the :doc:`Predictions <../evaluation/predictions>` widget. We want to see the quality of LR prediction model for a person being a republican or a democrat, based on their voting patterns. In :doc:`Select Columns <../data/selectcolumns>` we choose logistic regression as the feature and party as the class. Then we use the :doc:`Scatterplot <../visualize/scatterplot>` to see which instances were correctly predicted and which were false.

.. figure:: images/LogisticRegression-example.png