Assign Multiple Variables
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Zach
le 28 Sep 2011
Commenté : Walter Roberson
le 15 Avr 2023
I have a array for example [1,2,3,4]. I want to assign a variable to each number in the array such that a=1, b=2, c=3, and d=4. I know I can do each one separately but I want to know if it is possible to this in one line.
1 commentaire
Image Analyst
le 29 Sep 2011
Kind of reminded me of the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F though I'm not saying you don't have a valid reason for doing that - you may well have.
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Walter Roberson
le 28 Sep 2011
It is not possible in one statement. It is possible in two statements, which you could combine on one line.
t = num2cell([1,2,3,4]);
[a,b,c,d] = deal(t{:});
8 commentaires
Fangjun Jiang
le 14 Avr 2023
t = num2cell([1,2,3,4]);
[a,b,c,d] = deal(t{:})
[a,b,c,d] = t{:}
Walter Roberson
le 15 Avr 2023
Back in 2011 it was not possible in one statement, at least not without an inline subsref(). A few years ago, however, a hack became available:
[a,b,c,d] = struct('x', num2cell([1,2,3,4])).x
Plus de réponses (4)
Raziman Thottungal Valapu
le 1 Oct 2020
It is now possible to do this in one line cleanly
[a,b,c] = deal(1, "test", [1:5])
Gives me
a =
1
b =
"test"
c =
1 2 3 4 5
As expected
1 commentaire
Stephen23
le 1 Oct 2020
@Raziman Thottungal Valapu: no, that is not what the question is about. The question specifies that there is only one input array, but your code uses multiple separate inputs to deal. Not the same thing at all.
Viktor
le 1 Sep 2018
Modifié(e) : Viktor
le 1 Sep 2018
The one-liner I have been using is the following:
[a,b,c,d] = feval(@(x) x{:}, num2cell([1,2,3,4]));
(Don't claim it is my original idea, just felt it belongs to this thread. If it is posted elsewhere feel free to link it.)
2 commentaires
Daniel Birch
le 12 Sep 2018
Additionally, you can replace num2cell with any cell array of the right size, even one containing multiple data types. For example,
[a,b,c,d] = feval(@(x) x{:}, {rand(2), 5, 'hello', pi});
a
a =
0.9502 0.4387
0.0344 0.3816
b
b =
5
c
c =
hello
d
d =
3.1416
Stephen23
le 12 Sep 2018
Modifié(e) : Stephen23
le 12 Sep 2018
That is just subsref wrapped up in an anonymous function, which is then called by feval.
Here it is with subsref called directly:
>> [a,b,c,d] = subsref({rand(2), 5, 'hello', pi}, substruct('{}',{':'}))
a =
0.103676 0.814128
0.208758 0.092132
b = 5
c = hello
d = 3.1416
Dan Erwin
le 14 Avr 2023
Modifié(e) : Walter Roberson
le 14 Avr 2023
The thing we are trying to do is emulate the very useful Python idiom e.g.
a,b,c,d = [1,2,3,4]
In Matlab, if you create a function assignList.m as follows:
function varargout = assignList( inputArray )
for i = 1:length( inputArray)
varargout{i} = inputArray(i);
end
end
then you can do for example
[a,b,c,d] = assignList( [1,2,3,4] )
4 commentaires
Fangjun Jiang
le 14 Avr 2023
@Stephen23, not with array input directly. See my comments at the answer by @Walter Roberson. My point is that this funciton is uncessary. Plus, I can't resist the "Deal or No deal" pun, now that I realized it.
Dan Erwin
le 15 Avr 2023
I would not have written my post if I had noticed the earlier answer which recommended the contributed function matsplit, which is similar to mine but is more flexible when using multidimensional arrays.
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