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## -*- texinfo -*-
## @deftypefn  {} {count =} runlength (@var{x})
## @deftypefnx {} {[count, value] =} runlength (@var{x})
## Find the lengths of all sequences of common values.
##
## @var{count} is a vector with the lengths of each repeated value.
##
## The optional output @var{value} contains the value that was repeated in
## the sequence.
##
## @example
## @group
## runlength ([2, 2, 0, 4, 4, 4, 0, 1, 1, 1, 1])
## @result{}   2   1   3   1   4
## @end group
## @end example
## @seealso{run_count}
## @end deftypefn

function [count, value] = runlength (x)

  if (nargin < 1)
    print_usage ();
  endif

  if (! (isnumeric (x) || islogical (x)) || ! isvector (x))
    error ("runlength: X must be a numeric vector");
  endif

  if (iscolumn (x))
    x = x.';
  endif

  idx = [find(x(1:end-1) != x(2:end)), length(x)];
  count = diff ([0 idx]);
  if (nargout == 2)
    value = x(idx);
  endif

endfunction


%!assert (runlength ([2 2 0 4 4 4 0 1 1 1 1]), [2 1 3 1 4])
%!assert (runlength ([2 2 0 4 4 4 0 1 1 1 1]'), [2 1 3 1 4])
%!test
%! [c, v] = runlength ([2 2 0 4 4 4 0 1 1 1 1]);
%! assert (c, [2 1 3 1 4]);
%! assert (v, [2 0 4 0 1]);

## Test input validation
%!error <Invalid call> runlength ()
%!error runlength (['A'; 'B'])
%!error runlength (ones (2,2))