Index exceeds the number of array elements (1)

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Jonas Freiheit
Jonas Freiheit el 9 de Sept. de 2020
Comentada: Jonas Freiheit el 10 de Sept. de 2020
%When I try to perform a row interchange for 'b' vector It tells me it exceeds the no of array elements. This is an attempt to perform partial pivoting for matrix A and vector b separately.
Thanks
A = [1 2 3;4 2 -1; 3 2 3];
b = [1; 3; 2];
k = 1;
A = pivoting(A,k)
function [A, b, flag] = pivoting(A, b, k)
n = size(A,1);
flag = 0;
for k=1:n-1
[big, i]=max(abs(A(k:n,k)))
ipr=i+k-1
if ipr~=k
A([k,ipr],:)=A([ipr,k],:)
b([k,ipr])=b([ipr,k])
end
end
end

Respuesta aceptada

Kojiro Saito
Kojiro Saito el 9 de Sept. de 2020
It's because you're trying to manipulate b in line,
b([k,ipr])=b([ipr,k])
but, you're inputting as follows.
k = 1;
A = pivoting(A,k)
so, in function pivoting, b (second input variable) is scalar (1).
You just need to input three variables.
% A = pivoting(A,k)
A = pivoting(A,b,k)
  9 comentarios
Kojiro Saito
Kojiro Saito el 10 de Sept. de 2020
It's not possible only changing the bold text code because the funtion pivoting requires three inputs, so you need to modify input variables so that it allows two inputs.
Jonas Freiheit
Jonas Freiheit el 10 de Sept. de 2020
Alright that makes sense,
Thanks for the help Kojiro!

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