How to index function-matrices?

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TheOpenfield
TheOpenfield 2017-11-23
评论： TheOpenfield 2017-11-23
Take for example: f =@(x) [x,1;1,x]
If you evaluate the function f, you get a matrix in return. Is there any way, to index this matrix before evaluating it?
Like f(1,1) and so forth.
Indexing the matrix while evaluating doesn't work either: f(1)(1,1)
You still need to refer to the result: f1 = f(1); f1(1,1)
=1

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采纳的回答

Walter Roberson
Walter Roberson 2017-11-23
No, there is no way to index the matrix before evaluating it.
To index after evaluating it, define
INDEX2 = @(Matrix, R, C) Matrix(R,C);
Then
INDEX2(f(1), 1, 1)
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Walter Roberson
Walter Roberson 2017-11-23
As I said,
MINDEX = @(x, R, C) INDEX2(M(x), R, C)

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更多回答（1 个）

Andrei Bobrov
Andrei Bobrov 2017-11-23
function out = f(x,ii,jj)
a = [x,1;1,x];
out = a(ii,jj);
end
use
>> f(1,1,1)
ans =
1
>>
  1 个评论
TheOpenfield
TheOpenfield 2017-11-23
编辑：TheOpenfield 2017-11-23
This might be it!
Now i can do further calulations, without loosing the function characteristics, like:
g = @(x) x*f(x,1,1)
There might be still another problem:
In my case, my function is set up as a multiplication of matrices containing functions as entries. Like:
M = @(x) f(x)*f2(x)...
The multiplication of the matrices f, f2 is done while evaluating M at any point.
Is there any easy way to index this function too even though M doesn't know about its matrix properties before evaluation?

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