Assign Multiple Variables

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Zach
Zach on 28 Sep 2011
Commented: Walter Roberson on 15 Apr 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 Comment
Image Analyst
Image Analyst on 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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Accepted Answer

Walter Roberson
Walter Roberson on 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 Comments
Fangjun Jiang
Fangjun Jiang on 14 Apr 2023
t = num2cell([1,2,3,4]);
[a,b,c,d] = deal(t{:})
a = 1
b = 2
c = 3
d = 4
[a,b,c,d] = t{:}
a = 1
b = 2
c = 3
d = 4
Walter Roberson
Walter Roberson on 15 Apr 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
a = 1
b = 2
c = 3
d = 4

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More Answers (4)

Raziman Thottungal Valapu
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 Comment
Stephen23
Stephen23 on 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.

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Jeff Miller
Jeff Miller on 15 Aug 2018
matsplit does this.
  2 Comments
Brent F
Brent F on 19 Jun 2021
Much cleaner than deal(a(1), a(2), a(3), a(4), ...)

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Viktor
Viktor on 1 Sep 2018
Edited: Viktor on 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 Comments
Daniel Birch
Daniel Birch on 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
Stephen23 on 12 Sep 2018
Edited: Stephen23 on 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

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Dan Erwin
Dan Erwin on 14 Apr 2023
Edited: Walter Roberson on 14 Apr 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 Comments
Fangjun Jiang
Fangjun Jiang on 14 Apr 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
Dan Erwin on 15 Apr 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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