Hello fellows and folks.

I have been looking to do this for 1 month and still cannot find the way to do it.

Here’s what’s going on:

I have a csv file called ratings.csv with the following structure:

userID, movieID, rating
3,  12, 5
2, 7,  4

The rating scale goes from 0 to 5 stars. I want to be able to plot the sparsity of the matrix like it’s done in the following picture:


As you can see, ratings scale goes from 0 to 5 on the right. It is a very well thought plot.

I have Matlab, Python, R etc. Could you come up with something and help me? I’ve tried hard but I cannot find the way to do it.

  • 2
    $\begingroup$ I don't understand you question. Do you want to repeat the plot? $\endgroup$ – nicoguaro May 20 at 0:08
  • $\begingroup$ Yes, exactly! Thats the idea but I cannot find the way to do it. $\endgroup$ – naveganTeX May 20 at 0:28
  • 3
    $\begingroup$ Anyway, your picture looks like it is simply the output of Matlab's imagesc(A), once you have converted the ratings to a sparse matrix A (which, I assume, you know how to do with spconvert or the three-argument version of sparse). $\endgroup$ – Federico Poloni May 20 at 12:23
  • 1
    $\begingroup$ Is your answer supposed to be an update to your post? $\endgroup$ – nicoguaro May 20 at 15:30
  • 1
    $\begingroup$ You just added code without any explanation, consider adding an explanation. Also, mentioning why @FedericoPoloni solution does not work. $\endgroup$ – nicoguaro May 20 at 15:51

I was able to do it this way though it may had been easier to plot it the way Federico has mentioned before: imagesc(A).

I declared an A matrix of zeros of mxn dimension and then loaded the ratings. I then applied HeatMap(A) which yields the image below.

A = importdata('u.data');
user_id = A(:, 1);
movie_id = A(:, 2);
rating = A(:, 3);

% Build matrix R 
R = zeros(943, 1682);

for i=1:100000
R(user_id(i), movie_id(i)) = rating(i);


m = HeatMap(R,’Xlabel’,’I did it!’)
ax = hm.plot; % 'ax' will be a handle to a standard MATLAB axes.
colorbar('Peer', ax); % Turn the colorbar on
caxis(ax, [0 5]); % Adjust the color limits

enter image description here


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