Subscript indices must either be real positive integers or logicals.

    if true
      % code
    end  
  function [Ex,Ey,Ez]=coordxtr(Edof,Coord,Dof,nen)
  %[Ex,Ey,Ez]=coordxtr(Edof,Coord,Dof,nen)
  %-------------------------------------------------------------
  % PURPOSE
  %    Extract nodal coordinate data from the global coordinate 
  %    matrix for a number of elements with equal number of 
  %    element nodes and dof's. 
  %
  % INPUT:  Edof :  topology matrix , dim(t)= nie x ned+1
  %                         nie= number of identical elements
  %                           ned= number of element dof's  
  %
  %         Coord: global coordinate matrix 
  %
  %         Dof:   global nodal dof matrix 
  %
  %         nen:   number of element nodes
  %
  % OUTPUT: Ex,Ey,Ez : element coordinate matrices
  %         Ex=[x1 x2 ...xnen;    one row for each element
  %             ...     ...  ;
  %             nel     ...  ]  
  %             dim= nel x nen ;   nel:number of elemnts 
  %-------------------------------------------------------------

% LAST MODIFIED: P-E Austrell 1993-10-14 
% Copyright (c)  Division of Structural Mechanics and
%                Department of Solid Mechanics.
%                Lund Institute of Technology
%-------------------------------------------------------------
    [nel,dum]=size(Edof);
     ned=dum-1;
    [n,nsd]=size(Coord);
    [n,nd]=size(Dof);
     nend=ned/nen;
 %
    for i = 1:nel
       nodnum=zeros(1,nen);
       for j = 1:nen
          check=Dof(:,1:nend)-ones(n,1)*Edof(i,(j-1)*nend+2:j*nend+1);
          [indx,dum]=find(check==0);
           if length(indx)>0
              nodnum(j)=indx(1);
           else
              nodnum(j)=0;
           end
      end
 %       
          Ex(i,:)=Coord(nodnum,1)';
       if nsd>1
          Ey(i,:)=Coord(nodnum,2)';
       end
       if nsd>2    
          Ez(i,:)=Coord(nodnum,3)';
       end
    end  
%--------------------------end--------------------------------

what should I do?

Thank you guys

??? Subscript indices must either be real positive integers or logicals.
    Error in ==> coordxtr at 49
              Ex(i,:)=Coord(nodnum,1)';

Answer 1

[Matt J]

In MATLAB indexing starts at 1, not 0, so setting nodnum to zero

nodnum(j)=0;

doesn't make sense if you are going to be indexing with it.

[Matt J]

Aside from that, it is appropriate that you invest some time reading about the DBSTOP command and other MATLAB debugging tools.

Most of the questions in your profile are simply requests for the forum to do basic debugging for you. That's not what it's for. The problems you've been having are easily troubleshot using the above referenced tools.

[Hamid]

thanks