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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) 2001 - INRIA - Carlos Klimann
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
//
function [s]=center(x,orient)
//
//This function computes s, the centered version of the
//numerical matrix x.
//
//For a vector or a matrix x, s=center(x) returns in the
//(i,j) coefficient of the matrix s the value
//(x(i,j)-xbar), where xbar is the mean of the values of
//the coefficients of x.
//
//s=center(x,'r') (or, equivalently, s=center(x,1)) is the
//rowwise center reduction of the values of x. It returns
//in the entry s(i,j) the value (x(i,j)-xbarv(j)) with
//xbarv(j) the mean of the values of the j column.
//
//s=center(x,'c') (or, equivalently, s=center(x,2)) is the
//columnwise centre reduction of the values of x. It
//returns in the entry s(i,j) the value (x(i,j)-xbarh(i))
//with xbarh(i) the mean of the values of the i row.
//
[lhs,rhs]=argn(0)
if (rhs<1)|(rhs>2) then error(msprintf(gettext("%s: Wrong number of input arguments: %d to %d expected.\n"),"center",1,2)), end
if x==[] then s=%nan, return, end
[m n]=size(x);
if rhs==1
xbar=(sum(x)/(m*n))
s=x-(ones(m,n)*xbar)
elseif orient=="c"|orient==2 then
xbar=sum(x,"c")/n
s=x-(xbar*ones(1,n))
elseif orient=="r"|orient==1 then
xbar=sum(x,"r")/m
s=x-(ones(m,1)*xbar)
else error(msprintf(gettext("%s: Wrong value for input argument #%d: ''%s'', ''%s'', %d or %d expected.\n"),"center",2,"r","c",1,2)),
end
endfunction
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