heatmapdemo.m

Heat maps with numeric values overlayed

%% Annotated Heat Maps 
% A number of people have asked me whether MATLAB can add text to heatmaps
% to show the exact values. This is very easy to do, however, making a the
% text robust to resizing, zooming and other operations is a little
% trickier.

%% A basic heat map
% The *image* command or *imagesc* command can be used to create heat maps.
% The difference between the two functions is that *imagesc* scales the
% colormap of the image to give the maximum range of colors. For this
% example I will use some of the matrices in *gallery*. 

data = gallery('invhess',20);
imagesc(data)
axis off


%% Adding text
% When the heat map is small, it is sometimes convenient to see the actual
% data values on the image. These are easy to add using the *text*
% function.

[rows,cols] = size(data);
for i = 1:rows
    for j = 1:cols
                 textHandles(j,i) = text(j,i,num2str(data(i,j)),...
                'horizontalAlignment','center');
    end
end

%% Problems with this basic method
% This is fine until you resize the figure or zoom in. The font size for the text is
% fixed so the image quickly gets messy if you make it small. 
set(gcf,'position',[100,100,300,300])

%% A function to work around this problem
% around this I have created a function *heatmaptext* that adds listeners
% to the figure that adjust the font size of the text if the figure is
% resized or if you zoom in on the heat map.
figure
heatmaptext(data);


%%
% This function is robust to resizing of the figure.
set(gcf,'position',[100,100,300,300])

%% Some more examples

figure
data = randn(40,20);
heatmaptext(data,'fontcolor','w','precision',3);
colormap(redgreencmap)
set(gca,'Xlim',[4.5,10.5],'Ylim',[5.5,9.5]);

%% 

figure
data = gallery('moler',25);
heatmaptext(data,'fontcolor','r');
colormap(bone)



%%
%   Copyright 2007 The MathWorks, Inc.