How do I create a heatmap filled with NaN values for preset value of rows and columns?

I am making multiple heat maps with varying amounts of data. I want to create a blank heatmap of NaN values so all of my maps are 30x15, even if there isn't that much data in each.

How should I go about doing this?

Answer 1

[dpb]

HM=heatmap(nan(30,15));

You don't need such; just fill in an array of that size with the actual data at some point chosen for the upper RH corner for the real data to reside.

HR=30; HC=15;
A=nan(HR,HC);
R=20; C=10;
r=floor((HR-R)/2);
c=floor((HC-C)/2);
M=randi(200,[R,C]);
A(r:r+R-1,c:c+C-1)=M;
heatmap(A)

[KD]

thanks! I was forgetting the NaN!

[Steven Lord]

If you want the data to be centered and you're using release R2023b or later, you can use the paddata function.

A = randi(10, 12, 17);
P1 = paddata(A, [30 28], FillValue = NaN);
P2 = paddata(A, [30 28], FillValue = NaN, Side = "both");
figure
heatmap(A)

●

figure
heatmap(P1, Title="A is in upper-left corner")

figure
heatmap(P2, Title="A is centered")

[dpb]

P1 = paddata(A, [30 28], FillValue = NaN);
P2 = paddata(A, [30 28], FillValue = NaN, Side = "both");

When was the NamedParameterName=Value syntax introduced Steven? That surely confused an old fogey like me for a while until I figured it must be equivalent to and tried

P1 = paddata(A, [30 28], 'FillValue',NaN);
P2 = paddata(A, [30 28], 'FillValue',NaN, 'Side',"both");

to be certain. :)

As we've noted before, I'm still on R2021b for IT conflict-avoidance issues...