function A = etchg(A,E,i,j,d)

% ETCHG Change entries of matrices of polynomials in long format.
%	A = ETCHG(A,E,i,j) substitutes the rows of E for the (i,j) 
%	entries of an m-by-n matrix of polynomials stored in an 
%	(m*n + 2)-by-(k+1) matrix (long format). 
%	k is the highest degree of the polynomials in A. 
%
%	ETCHG(A,E,i,j,d) assumes that E contains only integers and
%	uses d as the common denominator of the entries in E.
%
%	See also ELCHG, PRTV

%	Written by Serge Tchikanda 06/14/96.
%       Last revised by Serge Tchikanda 06/17/96.

[m,n]=psize(A);
if isempty(m) | isempty(n)
   return
end
if strcmp(':',i)
   i = 1:m; 
end
if  strcmp(':',j)
   j = 1:n; 
end

idx = etplf(A,i,j);
if isempty(idx)
   return
end

D = A(2,1);
[m1,n1]=size(A);
[mE,nE]=size(E);

if mE ~= (length(i))
   disp(' ')
   disp('   The number of (i,j) entries must agree')
   disp('   with the number of rows of the second input.')
   return
end

if nE < n1
   E = [zeros(mE,n1-nE) E];
elseif nE > n1
   A(1:2)=[0;0];
   A = [zeros(m1,nE-n1) A];
   A(1:2) = [m;D];
end

if nargin < 5
   [num,den]=rat(E);
   d=matlcm(den);
   A(idx,:)=E*D;
   A(2:m1,:)=A(2:m1,:)*d;
else
   A(2:m1,:)=A(2:m1,:)*d;
   A(idx,:)=E*D;  
end

A = prtv(A,':',':');  % In case d was not gcd(E)