I think what you want is to produce a histogram with data that already contains the bin counts rather than using the histogram function to count the number of values within each bin.
If my interpretation is correct, use the syntax, histogram('BinEdges',edges,'BinCounts',counts)
Example
binEdges1 = [0 1 2 3 4 5]; % 5 bins, 6 edges
counts1 = [9 8 7 6 5]; % counts
binEdges2 = [2 3 4 5 6 7];
counts2 = [5 6 7 8 9];
figure()
hold on % <-- important
histogram('BinEdges',binEdges1,'BinCounts',counts1)
histogram('BinEdges',binEdges2,'BinCounts',counts2)
Or perhaps you want the grouped option with bar plots,
bar([hcx(:),hcy(:)],'grouped')
