Sometimes heatmap does not display decimal values

I have data sets representing pressures. These are represented by a matrix of 16 x 16 x 400(ish), representing a time pressure sequence of 400 temporally-ordered frames of a 16 x 16 array of 256 pressure sensors. I wanted to display the time maximum (using heatmap()) for each pressure sensor, and that worked exactly as expected. I display two alternative data sets side by side (using subplot), and get theit color-mapped squares with values, as expected. If instead I look at the temporal average, I only get the color mapped squares without the the decimal values.

If I insert a breakpoint, and issue:

heatmap(peaks1); colormap default

or

heatmap(av1); colormap default

both work as expected, but the following code:

            f=figure;
            f.Position = [0 128 1920 1280];
            peaks1 = max(p_seq1, [], 3);
            peaks2 = max(p_seq2, [], 3);
            av1 = mean(p_seq1, 3);
            a2 = mean(p_seq2, 3);
            
            subplot(1,2,1);
%            heatmap(av1);
            heatmap(peaks1); % displays text correctly
            colormap default
            title([gait, ' - ', horse, ' (OS)']);

            subplot(1,2,2);
            heatmap(av2); % displays no text
%            heatmap(peaks2);
            colormap default ;
            title([gait, ' - ', horse, ' (EQ)']);
            filename = [horse, ' - ', gait, '.jpg']
            saveas(f, filename);

doesn't display text for the av1 heatmap.

To further confuse things, one out of the 20 or so datasets I am using does display the average values, but I have no idea why.

Both the av and the peak show in the workspace as 16x16 double.

Thoughts?

[Mathieu NOE]

hello

can you share some of the data that create the issue ?

also I notice that you want to display av2 but you compute a2 so I wonder if av2 is actually defined

a2 = mean(p_seq2, 3);

heatmap(av2); % displays no text

[Peter Fraser]

Sorry Mathieu, the "a2" was just sloppy editing by me. The actual code has "av2". I think that I have worked out what's going on. The averaged data typically have three more digits than the peak data (being averaged over ~400 samples). heatmap() wants to display all of these, reducing the size of the typeface to do so. If it considers the typeface too small to display, it just silently decides to not display anything.

If I use:

heatmap(round(av2 * 10)/10);

I get the result I want.

Thanks

[Mathieu NOE]

at least problem solved !!

[Peter Fraser]

Yes! I first tried the multiply-round-divide trick in the command window, and it didn't work (it gives four places after the decimal point, with the last three "zero". Fortunately it does work with heatmap.

Answer 1

[Benjamin Kraus]

@Peter Fraser: The text in the cells in a heatmap hide themselves automatically when they get "too small". If you don't specify a FontSize, heatmap will look at the size of each cell and the size of the text that needs to be displayed, and calculate the FontSize necessary to fit the text into the cell. If that calculated FontSize is smaller than 6pt, then the labels are hidden.

There is no way to directly disable this behavior, or control the "minimum font size", but there is a workaround, which is to set the FontSize. By specifying the FontSize you disable both the automatic calculation of the FontSize as well as the automatic decision of whether to hide the text or not.