MATLAB: Replacing matrix rows in a loop

MATLABmatrix

Hi,

I am trying to build a n*k matrix but each row are produced by a function which has a 1*k output. How can I build that? I tried to build a n*k matrix of zeros and replace rows in a loop but since the dimensions are not same, I can't replace rows!

Thanks

Best Answer

X = zeros(100,10);      %preallocate
for ii = 1:size(X,1)    %loop over 100 rows
  X(ii,:) = rand(1,10); %insert 10 random numbers
end

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MATLAB: Hi am working on a code for gaussian elimination

The correct function is:

function [x,U]=gausselim(A,b)
% function to perform gauss eliminination
%FORWARD ELIMINATION
n=length(b);
m=zeros(n,1);
x=zeros(n,1);
for k =1:n-1;
      %compute the kth column of M
      m(k+1:n) = A(k+1:n,k)/A(k,k);
      %compute
      %An=Mn*An-1;
      %bn=Mn*bn-1;
      for i=k+1:n
          A(i, k+1:n) = A(i,k+1:n)-m(i)*A(k,k+1:n);
      end;
      b(k+1:n)=b(k+1:n)-b(k)*m(k+1:n);
end
U= triu(A);
%BACKWARD ELIMINATION
x(n)=b(n)/A(n,n);
for k =n-1:-1:1;
      b(1:k)=b(1:k)-x(k+1)* U(1:k,k+1);
      x(k)=b(k)/U(k,k);
end
end

After this try to run the code:

A=rand(5,4);
b=rand(4,1);
[x,U] = gausselim(A,b)

Is this what you want? I hope this helps...

George

Best Answer

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