How do I plot a matrix of ratings? I have a .csv file called ratings.csv with the following structure:

userID, movieID, rating
3,      12,      5
2,      7,       6


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.
You're looking for a heatmap. Check out e.g. https://stackoverflow.com/q/33282368/3924118 (if you like Python more than the others). See also this documentation.