Matrix Sampler
==============

.. figure:: icons/matrix-sampler.png

Samples a relation matrix.

Signals
-------

**Inputs**:

-  **Data**

Data set.

**Outputs**:

-  **In-sample Data**

   Selected data.

-  **Out-of-the-sample Data**

   Remaining data.

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

This widget samples the input data and sends both the sampled and the
remaining data to the output. It is useful for evaluating the
performance of recommendation systems.

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

1. Select the desired *sampling method*:

   -  **rows** (randomly samples entire matrix rows)
   -  **columns** (randomly samples entire matrix columns)
   -  **rows and columns** (samples from the entire matrix)
   -  **entries** (randomly samples individual matrix elements)

2. Select the proportion of the data you want at the output.
3. Press **Apply** to commit the changes.

Example
-------

**Matrix Sampler** widget samples data into two subsets: in-sample and
out-of-the-sample data. This is useful if you want to check the accuracy
of matrix reconstruction with **Completion Scoring**. Feed in-sample
data into the **Fusion Graph** to reconstruct the matrix and then
compare the results with out-of-the-sample data.

.. figure:: images/MatrixSampler-Example2.png