Array indices must be positive integers or logical values

H = 0;
M = length(h);

for k=0:M-1
    H = H + (h(k) * exp(-1i*2*pi*fd));
end
%fd and h come from a function call

Answer 1

[Star Strider]

The problem:

for k=0:M-1

The solution:

for k=1:M

In MATLAB, subscript indices begin at 1, not 0, and are defined as integers greater than 0.

It is more efficient to do this without the loop:

H = cumsum(h* exp(-1i*2*pi*fd));

or simply:

H = sum(h* exp(-1i*2*pi*fd));

Answer 2

[Fabio Freschi]

Your index k starts from 0 and you are indexing h with k, so you are asking at the first iteration h(0). Matlab has 1-indexing so you get the error. I guess your for loop should be

for k = 1:M
    ...
end