What is M(I) where M is a real matrix and I is a matrix of indices.

M is a 67x67 matrix of doubles. I is a 441x2 matrix, with I = [xc,yc]. Each row is a pair i,j of indices of M. I want to apply M to I and get a vector of 441 doubles. However, M(xc,yc) gives a matrix of size 441x441 and M([xc,yc]) gives a matrix of size 441x2. I think both results give only zeros. Does anyone know what is happening, as there is no error message? The only thing I can think of is to convert to linear indices. Is that the only way?

Answer 1

[Stephen23]

"The only thing I can think of is to convert to linear indices. Is that the only way?"

Yes. Use sub2ind.