Indexing of fresh array in one line without intermediate variable.

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Maxim
Maxim 2013-6-6
回答： DH 2023-12-28
How do I index a newly made array without intermediate variables?
Maybe not the best example, but imagine I want to do this
regexp(string,expression,'match')(10:20)
How do I do it in one line?
It is not a regexp question. This problem occurs in many different situations. Thank you
EDIT Another example
function ans = Func(array)
array
end
I want it to look like
Func(1:10)(2:3)
But I need to do
temporary = Func(1:10);
temporary(2:3)
EDIT2. Finally found the answer here: http://stackoverflow.com/questions/3627107/how-can-i-index-a-matlab-array-returned-by-a-function-without-first-assigning-it
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UniqueWorldline
UniqueWorldline 2017-11-14
For anyone finding this question as late as I have, but who is looking for a simple solution for the
size
function, do the following to only get the one index of the array size you are looking for:
A = [1,2,3,4,5]; % Some array
arrayCols = size(A); % This returns a 1x2 array with the number of rows
% and columns of A. Which is undesirable if only
% the columns are wanted. Instead do this:
[arrayRows,arrayCols] = size(A);
Now arrayCols is a scalar value that can be used immediately. This doesn't allow you to do
size(A)(2)
but it can still eliminate an intermediate.
Stephen23
Stephen23 2023-11-9
编辑：Stephen23 2023-11-9
Ran in:
"This returns a 1x2 array with the number of rows and columns of A."
No. Strictly speaking that actually returns the combined size of all dimensions >=2. Lets try it now:
A = rand(5,4,3);
[rows,notcolumns] = size(A)
rows = 5
notcolumns = 12
If you really want the number of columns only then the simple and reliable approach is this:
size(A,2)
ans = 4

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采纳的回答

Maxim
Maxim 2013-6-6
编辑：Maxim 2013-6-6
From http://stackoverflow.com/questions/3627107/how-can-i-index-a-matlab-array-returned-by-a-function-without-first-assigning-it
Problem
magic(5)(3)
Solution 1
value = subsref(magic(5),struct('type','()','subs',{{3,3}}));
Solution 2
paren = @(x, varargin) x(varargin{:});
paren(magic(5), 3, 3);
  2 个评论
Jose Daniel Ortiz
Jose Daniel Ortiz 2018-9-18
So, basically, Matlab does not really support execution and indexing in the same line. This is in contrast to python, in which you can have ludicrously and arbitrarily complex chains of computation in a single line such as:
thing = A(B(size(A)(0))(0))
Walter Roberson
Walter Roberson 2020-2-6
MATLAB does "really" support execution and indexing in the same line, but the syntax for it is pretty ugly. And you need a real assignment in order to capture any output after the first output from a function that returns multiple outputs.

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更多回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-6-6
编辑：Azzi Abdelmalek 2013-6-6
Look at
cellfun
arrayfun
Example
a=[2 3 5 8]
out=arrayfun(@(x) x^2+sin(x),a)
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Maxim
Maxim 2013-6-6
I know these functions, but don't see how they could be helpful. The problem is that I can't index the fresh array.

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DH
DH 2023-12-28
Hope this helps.
interp1(Func(1:10), 2:3)

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