MATLAB Examples

# t-SNE Custom Output Function

This example shows how to use an output function in tsne.

## Custom Output Function

The following code is an output function that performs these tasks:

• Keep a history of the Kullback-Leibler divergence and the norm of its gradient in a workspace variable.
• Plot the solution and the history as the iterations proceed.
• Display a Stop button on the plot to stop the iterations early without losing any information.

The output function has an extra input variable, species, that enables its plots to show the correct classification of the data. For information on including extra parameters such as species in a function, see docid:matlab_math.bsgprpq-5.

```function stop = KLLogging(optimValues,state,species)
persistent h kllog iters stopnow
switch state
case 'init'
stopnow = false;
kllog = [];
iters = [];
h = figure;
c = uicontrol('Style','pushbutton','String','Stop','Position', ...
[10 10 50 20],'Callback',@stopme);
case 'iter'
assignin('base','history',kllog)
iters = [iters; optimValues.iteration];
if length(iters) > 1
figure(h)
subplot(2,1,2)
plot(iters,kllog);
xlabel('Iterations')
subplot(2,1,1)
gscatter(optimValues.Y(:,1),optimValues.Y(:,2),species)
title('Embedding')
drawnow
end
case 'done'
% Nothing here
end
stop = stopnow;

function stopme(~,~)
stopnow = true;
end
end

```

## Use the Custom Output Function

Plot the Fisher iris data, a 4-D data set, in two dimensions using tsne. There is a drop in the Divergence value at iteration 100 because the divergence is scaled by the exaggeration value for earlier iterations. The embedding remains largely unchanged for the last several hundred iterations, so you can save time by clicking the Stop button during the iterations.

```load fisheriris rng default % for reproducibility opts = statset('OutputFcn',@(optimValues,state) KLLogging(optimValues,state,species)); Y = tsne(meas,'Options',opts,'Algorithm','exact'); ```