How to plot a histogram in 2D if one has the counts already?

I collected some 2D histcounts with

histcounts2

now that I have the counts, how do I plot them? I know one can just feed the actual data X to hist3 but unfortunately that is not an feasible option because I suspect it would make matlab crash. I essential pre-compute the histogram counts for my data first because its more memory efficient (or at least doesn't crash matlab).

For a snippet of my code:

Xedges = linspace(lb,ub,nbins);
Y_edges = linspace(lb,ub,nbins);
W_hist_counts_all = zeros( size(nbins,nbins) );
index = 1;
for file_struct = data_filenames'
    if ~( strcmp(file_struct.name,'.') || strcmp(file_struct.name,'..') || strcmp(file_struct.name,'.DS_Store') )
        load( [path file_struct.name] );
        w1 = W_history(:,1);
        w2 = W_history(:,2);
        current_W_hist_counts = histcounts2(w1,w2,Xedges,Yedges);
        W_hist_counts_all = W_hist_counts_all + current_W_hist_counts;

then I just wish to plot:

W_hist_counts_all

any ideas how?

Answer 1

[Steven Lord]

If you're using release R2016b or later, you can "Create a histogram from precomputed bin counts". The specific signature you want is histogram2('XBinEdges',Xedges,'YBinEdges',Yedges,'BinCounts',counts)

[Brando Miranda]

thanks! Not sure if I missed it or something, but shouldn't this info be in the main pages of these functions? I mean who wants the counts and then not do anything with them?

[Steven Lord]

That syntax is listed in the middle of the Description section on the histogram2 documentation page. I literally copied and pasted it from there into my message. If you have a suggestion for how we can improve the visibility of that syntax I encourage you to click the "No" button in the lower-right corner of the documentation page where it asks "Was this topic helpful?" and share your suggestion in the feedback form. I know our documentation staff reviews that feedback on a regular basis.

[Brando Miranda]

thanks! I will. My complaint was on histcounts2 not histogram2 though.

[Steven Lord]

Perhaps I'm not understanding your complaint, but the whole purpose of histcounts2 is to compute the bin counts. If you already have the bin counts, you don't need to call histcounts2 at all.

It would be like sending your friend a text message complaining that you have to find your cell phone ... using your cell phone.