Matlab中系列的总和

Question

I would like to run this function in Matlab:

where z is a [N1xN2] matrix, x is a [M1xM2] matrix and y is a [P1xP2] matrix.

N1=M1+P1-1 and N2=M2+P2-1

I am now trying to do it using 4 for-loops which might be quite time consuming for large matrices.

I found symsum() function in Matlab but I cannot see how to adjust it to work for double sums. Is there an easier way to do it?

Answer 1

The formula which you are trying to calculate is 2D discrete convolution.

In Matlab, there is a function which calculates it automatically, it is called conv2.

Use the following code:

Z = conv2(x,y);