Subscript indices must either be real positive integers or logicals?

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Nearlight_lovegym 2018-3-4

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https://ww2.mathworks.cn/matlabcentral/answers/386198-subscript-indices-must-either-be-real-positive-integers-or-logicals

回答： Ahmet Cecen 2018-3-4

采纳的回答： Ahmet Cecen

Hello, I'm trying to define the Sherman-Morrison formula:

using the code

invA = A.^(-1)

n=size(A,1)

u=ones(n,1)

Z = 1 + u'*invA*u

inv(A + u*u')=invA - 1/Z * invA * u*u' * invA.

I'm using Z here instead of alpha in the problem. It always returns to an error "Subscript indices must either be real positive integers or logicals". What does it mean? Can somebody help with it??

Matlab new starter here, all help would be appreciated. Thanks heaps!!

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Answer 1

Ahmet Cecen 2018-3-4

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There is a more fundamental issue here:

inv(A + u*u')=invA - 1/Z * invA * u*u' * invA

The above line indicates that you need to go over some basic MATLAB tutorials. You can't just type and equation with variables on both sides and solve it like you would in Maple or Mathematica. While:

New = inv(A + u*u')

is a perfectly valid line:

inv(A + u*u') = New

is not.