--- /dev/null
+## Copyright (C) 2010 Mark Borgerding <mark@borgerding.net>
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{outdata} =} helintrlv (@var{data}, @var{col}, @var{ngrp},@var{stp})
+## @var{col}-by-@var{ngrp}.
+## @seealso{heldeintrlv}
+## @end deftypefn
+
+function [outdata,outstate] = helintrlv(data,col,ngrp,stp,init_state)
+
+ if (nargin < 4 ||nargin>5)
+ error('usage : interlvd = helintrlv(data,col,ngrp,stp)');
+ end
+
+ if(~isscalar(col) || ~isscalar(ngrp))
+ error("col and ngrp must be integers");
+ end
+
+ if( col ~= floor(col)|| ngrp ~= floor(ngrp))
+ error("col and ngrp must be integers");
+ end
+
+ didTranspose=0;
+ if ( isvector(data) && columns(data) > rows(data) )
+ data = data.';
+ didTranspose=1;
+ end
+
+ s = size(data);
+
+ if s(1) ~= col*ngrp
+ error("The length of data must be equals to ngrp*col");
+ end
+
+ if nargin==4
+ init_state = zeros(stp*col*(col-1)/2,s(2));
+ end
+
+ outstate =[];
+ # for each column
+ for k = 1:s(2)
+ tmp = reshape( data(:,k) , ngrp, col );
+ instate = init_state(:,k);
+ outstateCol=[];
+ for k1=2:col
+ curStepSize = (k1-1)*stp;
+ tmpCol= [instate(1:curStepSize) ;tmp(:,k1)];
+ tmp(:,k1) = tmpCol(1:ngrp);
+ outstateCol=[outstateCol;tmpCol(end+1-curStepSize:end)];
+ instate = instate(curStepSize+1:end);
+ end
+ outdata(:,k) = reshape(tmp.',s(1),1);
+ outstate = [outstate outstateCol];
+ end
+
+ if didTranspose
+ outdata = outdata.';
+ end