MATLAB Answers

Index exceeds the number of array elements (1)

조회 수: 6(최근 30일)
%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

  댓글 수: 0

댓글을 달려면 로그인하십시오.

채택된 답변

Kojiro Saito
Kojiro Saito 9 Sep 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)

  댓글 수: 9

표시 이전 댓글 수: 6
Jonas Freiheit
Jonas Freiheit 10 Sep 2020
Yeah, including this code with only changing from the bold text code.
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 %Here
[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 %End
Thanks, Kojiro
Kojiro Saito
Kojiro Saito 10 Sep 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 10 Sep 2020
Alright that makes sense,
Thanks for the help Kojiro!

댓글을 달려면 로그인하십시오.

추가 답변(0개)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by