Access a single element of an anonymous function that returns an array

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Leo Simon
Leo Simon 2014-4-27
评论： Stephen23 2020-4-20
I have an anonymous function that returns an array. I'd like to be able to create a new anonymous function that consists of a single element of this array WITHOUT using matlabfunction (which is infuriatingly restrictive in several respects).
For example, consider the following code (it's a ridiculously simple example, for expository purposes, obviously there are easy ways of dealing with this example, but my real problem is more complex)
y = sym('y',[1,4])
f = @(y)[y(1);y(2);y(3);y(4)]
f(y)
which returns
ans =
y1
y2
y3
y4
I'd now like to define a new anonymous function which extracts, say, the third element of this array. Obviously,
g = @(y) f(y)(3)
won't work. Is there some way to accomplish this? Again, solns involving matlabfunction are not satisfactory.
Any suggestions would be most appreciated!
Leo

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采纳的回答

Walter Roberson
Walter Roberson 2014-4-27
indexat = @(expr, index) expr(index);
g = @(y) indexat(f(y), 3);

更多回答（1 个）

Lauren Barr
Lauren Barr 2020-4-20
This is really helpful, thank you! I was wondering if there is a way to extend it, so that I can index one particular value in a 2D matrix, instead of indexing into a vector?
For example, this doesn't seem to work:
indexat = @(expr, index) expr(index);
g = @(y) indexat(f(y), (1,3));
But maybe I am missing something obvious.
Thank you!
Lauren

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