MATLAB: Plotting a variable as a function of the iteration number in a for loop

for loopiterationMATLABplotting

Hi,
Basically I have loop, within which is a 12X12 array of zeros and ones. For each cycle of the loop I need to sum the value of the array(which I am able to do) and then plot this value against the iteration/loop number.
Obviously the value of the array changes for each loop so I am a bit stuck as to how to plot the graph.
Eg. Do I output the values for each loop to a seperate new array/file, which I then draw upon at the end of the loop to create the graph? Or is there some way to construct a graph in stages as the program loops-essentially holding the plot figure and adding new points to the existing plot for each iteration.
Any help would be very much appreciated! If I have not explained very well just let me know and I can try and explain further/provide code snippets.
Thanks in advance,
Mike Scott

Best Answer

Here is an example. Note that if your loop index is 1-to-N, then you won't need the loop counter and this can be simplified in obvious ways. I do have to wonder, however, if you can avoid the loop altogether. Only a look at your code can shed light here...
lp_idx = 10:.5:30;  % This is the loop index.
S = zeros(1,length(lp_idx));  % Pre-allocation.
cnt = 1;  % Loop counter.
for ii = lp_idx
   t = magic(ii);  % An array which changes in loop
   S(cnt) = sum(t(:)); % The sum of each array
   cnt = cnt + 1;  % Increment the counter.
end
plot(lp_idx,S)  % Plot sum vs. loop index
xlabel('Loop Index')
ylabel('Matrix Sum')
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