Question

I have a loop calculating the variance, which I want to plot.

for k = [1:3]
disp(B.colheaders{1, k});
%disp(B.data(1:79, k + 1));
for j = [1:10:79]
    disp(j)
    Variance = var(B.data(j:j+8, k))
end
%disp(V)
plot(Variance)
end

How do I store the variances to an array or matrix so I can plot them all?

Answer 1

Here’s a way if you want to keep the loop:

figure,hold on %# avoid erasing the previous plots
for k = [1:3]
disp(B.colheaders{1, k});
%disp(B.data(1:79, k + 1));
startIdx = [1:10:79];
Variance = zeros(size(startIdx));
for j = startIdx
    disp(j)
    Variance(j==startIdx) = var(B.data(j:j+8, k))
end
%disp(V)
plot(Variance)
end

Here’s a way where you skip the inner loop

figure,hold on
for k = [1:3]
disp(B.colheaders{1, k});
%disp(B.data(1:79, k + 1));
startIdx = [1:10:79];
varIdx = bsxfun(@plus,startIdx,(0:7)'); %# create array for indexing

currentData = B.data(:,k);

%# calculate variance for each column
Variance = var(currentData(varIdx),1,1);

plot(Variance)
end