function l = ctxgroup(data)
% function l = ctxgroup(data)
%
% data  The incoming data should be a list generated by ctx2mat (or in the
%         same format).
%
% This function does some very basic processing of trial information.
% Only "valid/successful" trials are included in the output.
% The output is a list with the following format:
%
%  l{i}{j} == data for condition i, (successful) presentation j
%
% The contents of l{i}{j} are the same as the incoming data.
% This code relies on the Cortex header containing the proper flag
% as to whether the trial was successful or not. This must be explicitly
% done during the running of a Cortex program.
%
% Version 1.0
% For additional code, updated versions, questions or comments, please refer
% to the Active Perception Lab home page
%            http://www.cnbc.cmu.edu/~tai/lab.html


% Copyright 1998-1999
% Rick Romero
% rickr+@cmu.edu
% Permission to use and modify is granted,
% but not to redistribute original or modified code.



len = length(data);
maxCnd = 0;
trialCounts = [];
for i=1:len
  header = data{i}{1};
  if (header(12) == 0)
    % successful trial, get the info
    cndNum = header(1) + 1;
 
    if (length(trialCounts) < cndNum)
      trialCounts(cndNum) = 0;
    end
    trialCounts(cndNum) = trialCounts(cndNum) + 1;
    maxCnd = max([maxCnd; cndNum]);
  end
end

l = cell(maxCnd, 1);

for i=1:len
  header = data{i}{1};
  if (header(12) == 0)

    cndNum = header(1) + 1;
    if (isempty(l{cndNum}))
      l{cndNum} = cell(trialCounts(cndNum),1);
      trialCounts(cndNum) = 0;
    end
    trialCounts(cndNum) = trialCounts(cndNum) + 1;
    l{cndNum}{trialCounts(cndNum)} = data{i};
  end
end