title: Error with TSNE algorithm with malahanois distance in MATLAB
body: <p>I have the following code to plot my data using TSNE feature reduction algorithm in matlab</p>
  
  <pre><code>data=dlmread('features.txt');
  
  meas=data(:,2:end);
  species=data(:,1);
  
  rng('default'); % for reproducibility
  Y = tsne(meas,'Algorithm','exact','Distance','mahalanobis');
  gscatter(Y(:,1),Y(:,2),species);
  title('Mahalanobis');
  </code></pre>
  
  <p>However, by running it I have the following problem:</p>
  
  <blockquote>
    <p>The covariance matrix for the Mahalanobis metric must be symmetric and
    positive definite.</p>
    
    <p>Error in tsne (line 323)
            tempDistMat = pdist(X,distance);</p>
    
    <p>Error in plotafeatures (line 7) Y =
    tsne(meas,'Algorithm','exact','Distance','mahalanobis');</p>
  </blockquote>
  
  <p>With other distances the plot occurs correctly, what is possibly happening with my code or data?</p>
  
  <p>My data can be found <a href="http://www.ic.unicamp.br/~ra023169/features.txt" rel="nofollow noreferrer">HERE</a></p>