How do I ensure that my print command prints the figure that is on top at the time?
Simple, don't rely on the current figure since as you've discovered the current figure may not be the one you expect. Instead explictly capture the figure handle of the figure you want to print when you create it:
for k = 1:18
hfig = figure; %capture figure handle. Doesn't matter what gcf is, hfig will always be the figure we created
%...
flname = foldname + "\figure_" + hfig.Number));
print(hfig, flname, '-dpng');
end
Since the current figure can change, it may also be safer if you ensure that all your plots were directed to the correct figure/axes, so:
for k = 1:18
hfig = figure;
hax = axes(hfig); %guaranteed to be in the correct figure
surface(hax, X,Y,charvalues(:,:,k)); %guaranteed to be in the correct axes
view(hax, 3);
xlabel(hax, xstring);
ylabel(hax, ystring);
zlabel(hax, charlabels(k));
grid(hax, 'on');
flname = foldname + "\figure_" + hfig.Number));
print(hfig, flname, '-dpng');
end
