function [splits,splitvalues,notinanysplit] = makesplits (x,values)

% MAKESPLITS Partitions indices of a vector by their values
% splits = makesplits (x,[values])
% 
% x is a n-element vector
% values can be a cellarray or integer
%
%   if values is a cell array, then 
%      splits{k} has all indices j such that x(j) is in splitvalues{k} = values{k} 
%      splitvalues = values
%      notinanysplit has indices with all j such that x(j) is not in any values{i}.
%
%   If values is an integer k
%      splits{k} has all indices j such that x(j) is in splitvalues{k}
%      splitvalues is a k-element cell array representing the split created by makesplits. 
%        The values are split so that when concatenated, they are sort(unique(x)), and 
%        so the first k-1 splits are equal-sized.
%      notinanysplit = []
%
% If values is not supplied, it is assumed to be length(unique(x)).

% Dinoj Surendran dinoj@cs.uchicago.edu 12 Jun 05

iscol=1;% if x is a column vector
if (1==size(x,1))
  iscol=0;% if x is a row vector
end

ux = sort(unique(x));
if nargin<2,
  values=length(ux);
end

if isnumeric(values)
  k=values;
  lux = length(ux);
  a=ceil(lux/k);
  a_st = 1+a*[0:k-1];
  a_en = min(a*[1:k],lux);
  for i=1:k 
    splitvalues{i} = [ux(a_st(i):a_en(i))];
    splits{i} = find(x>=ux(a_st(i)) & x<=ux(a_en(i)));
  end
  notinanysplit = [];
else
  notinanysplit = [1:length(x)];
  for j=1:length(values)
    splits{j} = [];
    for k=1:length(values{j})
      fi = find(x==values{j}(k));
      notinanysplit = setdiff(notinanysplit,fi);
      if iscol
        splits{j} = vertcat(splits{j},fi);
      else
        splits{j} = horzcat(splits{j},fi);
      end
    end
  end
  splitvalues = values;
end