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

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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

Accepted Answer

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

More Answers (1)

Lauren Barr
Lauren Barr on 20 Apr 2020
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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