double indexing

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Frank
Frank 2012-1-12
评论： Petter 2023-7-11
Hello,
is it possible to do double or multiple indexing in matlab? E.g.
>> v = [1,2,5,7,9]
v =
1 2 5 7 9
>> v(1:4)
ans =
1 2 5 7
>> v(1:4)(2:3)
ans =
2 5
The first index create a new vector and the second index creates a new vector out of the newly created one. It is common in other languages, and it helps to avoid defining temp variables.
Cheers, Frank

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采纳的回答

Walter Roberson
Walter Roberson 2012-1-12
The closest you can get is
subsref(V(1:4), struct('type', '()', 'subs', 2:3)))
You can follow {} referencing by () referencing, {}(), but you cannot use ()() or (){} or ().{} or ().(), and you cannot use function(){} or function()() or function().field
  2 个评论
Frank
Frank 2012-1-12
thanks. Then I prefer to use a temp var instead. :)
Petter
Petter 2023-7-11
"You can follow {} referencing by () referencing, {}()"
This one line made my day so much easier, greatly appreciated. Thumbs up, gold star.

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更多回答（2 个）

mklcst mklcst
mklcst mklcst 2014-1-23
I think it could be very useful to have a short way to perform double indexing.
Jos (10584)
Jos (10584) 2014-1-23
If the indices are stored in variables, this is trivial!
V = [1,2,5,7,9]
ii = 1:4
jj = [2 3]
out = V(ii(jj))
  1 个评论
lee eugene
lee eugene 2019-8-2
However, if the two index do not have the same starting indexing, there would be something wrong. For example, i would like to select index [2,4] from [1,2,5,7,9] at first, and then select index [1,2]. Then it would be [2,5,7] at first and [2,5] in the end.

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