difficulties with basic syntax in array subsetting

Hi, I am trying to create a matrix of vectors from a larger array. Basically every time there is some stimulus (recorded as a 1 in a binary vector) I want to create a new array of the previous 150 timesteps from the corresponding ("response") vector. But I get the "Subscript indices must either be real positive integers or logicals" error messages. How can I best create the new array? I am a very basic Matlab user.

    for i=1:length(full_array)
        if binary_vec(i) == 1
            spike_vec(i) = response((i-150):i,1)
        end
    end

Answer 1

[dpb]

for i=151:length(full_array)
  if binary_vec(i)
    spike_vec = response((i-150):i)
  end
end

Your code had two basic issues --

1. If the response starts before the 150th observation subscript i-150 <= 0. I solved it by not starting the scanning until past the desired length. If that throws out real data, use max(i-150,1) to get the initial shorter lengths, and
2. The subscript on the result variable expression tries to put the RHS vector into a single location on the left; that can't work. The above solution works iff you process this set of observations before going on to the next; if you need to save these all as a separate array of some number of columns of length 150, then you need sotoo

j=j+1;       % increment column
spike_vec(:,j)=response(...  % save the subvector

If the indicator vector is indeed just a logical vector showing the locations; you can eliminate the loop over every element and use

ix=find(binary_vec);  % return starting locations

and then just select those positions from that vector.