How to extract columns from cells in a cell array

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I have tried many examples available online but I am still not quite able to get what I desire. So my cell array is 1 x 123 and in each cell, there is a data structure (matrix) of dimension 10 x 8. Now I want to extract column 3:4 into a matrix q and column 6:7 into a matrix p, in each of the 123 cells. I try this in a loop so that each time, the code goes into cell{1,n} and generates matrices p and q, then runs a function script (warp) on the matrices p and q generated and finally stores the output in a .mat file. I want the script to keep appending result scalars on the output file until the last cell. In the end, I want to have a 123 x 1 matrix of output scalars. Here is my code:

format short g
numfiles = 123;
output = zeros(numfiles, 1);
mydata = cell(1, numfiles);
for k = 1:numfiles
  filenames = sprintf('pid%d.xls', k);
  mydata{k} = importdata(filenames);
  a = mydata{1,k}.data; %I think this will only hold the kth cell data in the end.
  q = a(:, 3:4);
  p = a(:, 6:7);
  output = warp(p,q);
end

This code runs but honestly I am sure I am not doing things right from the line I generate the `a` variable. Indeed I only get a single scalar as results in the end. Please help.