create a function handle extracting pieces from a matrix function handle

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Sergio Codeluppi
Sergio Codeluppi 2013-6-4
I created a Matrix function using function handle @ like
A=@(x) [1 2 x; 2*x x.^2 3]; %it's an example
i need to create another function extracted from the previous one
B=@(x) A(x) without the second column
therefore size(A)=2x3 and size(B)= 2x2;
if it wasn't for the handle: B=A(:,[1 3])
ty for your help

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采纳的回答

Kye Taylor
Kye Taylor 2013-6-4
编辑：Kye Taylor 2013-6-4
Starting from your example
A = @(x) [1 2 x; 2*x x.^2 3];
you probably realized that this command is not allowed
B = @(x)[A(x)(:,1),A(x)(:,3)]
However, you can use this command:
B = @(x)[A(x)*[1;0;0],A(x)*[0;0;1]]

更多回答（1 个）

Walter Roberson
Walter Roberson 2013-6-4
B=@(x) subsref(A(x), struct('type', '()', 'subs', {':', [1 3]}));
Note: if the requirement is "all of whatever is there, except column 2", rather than "select only column 1 and column 3", then in order to avoid evaluating A(x) twice, one would have to add a helper anonymous function (because a subscript of 'end' is not allowed at the subsref level and must be converted to numeric form.)
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Sergio Codeluppi
Sergio Codeluppi 2013-6-4
i actually don't know command subsref, but tried your way and i get this
Error using subsref The "subs" field for the subscript argument to SUBSREF and SUBSASGN must be a cell or character array.
ty anyway for your help!

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