MATLAB: Storing variables without overwriting them

for loopMATLAB

Hello guys,
I made a piece of code that run through all the elements of each row and calculate the convolution. my problem is how can I store the previous answers without overwriting them
A=[1,2;3,4];
v=[1 -2 1];
y=[];
for i=1:length(A)
x=A(i,:);
for c=1:2
y=conv(v,x);
end
hold on
end
The result should be a matrix exp
result
1  0 -3  2
3 -2 -5  4
instead I only get the last row
3  -2 -5  4

Best Answer

Do this instead
y(i,:)=conv(v,x);
You should probably also preallocate the memory for y before the loop, like
y = zeros(2,4)
or however you would determine the final dimensions. "Growing" the array row-by-row is poor memory management in MATLAB, and can lead to significantly slower execution time for large arrays.
Also, I am not sure what you expect the "hold on" command to be doing there. That would only be related to plotting.
Related Question