Storing variables without overwriting them

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

Answer 1

[the cyclist]

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.

[Massi Friha]

Thank you very much sir :)