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Visualizing MovieLens Rating Matrix

It is interesting to look at the visualization of the MovieLens Rating Matrix

Here is a random sub sample

 

 

Here is the Matlab's code:

% load data
% Multi-character delimiters are not supported;
% so we get columns with delimeters too
D = importdata('ratings.dat',':');

% load data into sparse matrix
X = sparse(D(:,3),D(:,1),D(:,5));

% plot the whole matrix
imagesc(X'); figure(gcf)

% plot random sampling of matrix
r1_idx = randint(1,100,[1,6040]);
r2_idx = randint(1,100,[1,3592]);
R = X(r2_idx,r1_idx);
imagesc(R'); figure(gcf)