How to fix my my convolution function?

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Andrew
Andrew on 19 Mar 2014
Commented: Image Analyst on 19 Mar 2014
Hi, my teacher wants us to make a convolution function instead of using matlabs and this is what i have
x=[1 2 3 4] y=[1 2 3 4]
function P = MyConv1(x,y)
p = length(x); q = length(y);
for n = 1:p+q-1
for k = 1:n
P(n) = [sum(x(k)*y(n-k))];
end
end
however i get this error:
Attempted to access y(0); index must be a positive integer or logical.
Error in MyConv1 (line 11) P(n) = [sum(x(k)*y(n-k))];
someone please help me figure out what the issue is

Answers (1)

Image Analyst
Image Analyst on 19 Mar 2014
Then add 1. n-k is 0 and MATLAB doesn't allow a zero index. Try n-k+1.
  2 Comments
Andrew
Andrew on 19 Mar 2014
that did not work. And the formula for convolution states n-k so that is why I kept that.
this is the error with that
Attempted to access y(5); index out of bounds because numel(y)=4.
Error in MyConv1 (line 11) P(n) = [sum(x(k)*y(n-k+1))];
Image Analyst
Image Analyst on 19 Mar 2014
Just write the arrays down on paper. Slide them across and see what gets multiplied. It's not that hard to see what to do if you do that. If you really can't figure it out, come back.

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