.. _model.logit:

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

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

The logistic regression classification algorithm with LASSO (L1) or ridge (L2) regularization.

Signals
-------

**Inputs**:

-  **Data**

   A data set

- **Preprocessor**

   Preprocessing method(s)

**Outputs**:

-  **Learner**

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

-  **Logistic Regression Classifier**

   A trained classifier. Output signal sent only if input *Data* is present.

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

**Logistic Regression** learns a `Logistic Regression <https://en.wikipedia.org/wiki/Logistic_regression>`_ model from the data.

It only works for classification tasks.

.. figure:: images/LogisticRegression-stamped.png
   :scale: 50 %

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 prediction results with logistic regression on the *hayes-roth* data set. We first load *hayes-roth_learn* in the :doc:`File <../data/file>` widget and pass the data to **Logistic Regression**. Then we pass the trained model to :doc:`Predictions <../evaluation/predictions>`.

Now we want to predict class value on a new data set. We load *hayes-roth_test* in the second **File** widget and connect it to **Predictions**. We can now observe class values predicted with **Logistic Regression** directly in **Predictions**.

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