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%   my scripts for bits and pieces of the Tridiagonal demonstration
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function  rhs=setrhs(i,N)
% setrhs - sets the right hand side matrix for 1 on each end and a spike of one at index i
%   
  
  rhs=zeros(N,1); % start by make r a zero vector of length N
  rhs(1)=1; % set the height of tank 1 to 1
  rhs(N)=1; % set the height of tank N to 1
  rhs(i)=1;       % and put a flux of 1 in component  
  return