Assign Multiple Variables
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Zach
il 28 Set 2011
Commentato: Walter Roberson
il 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 Commento
Image Analyst
il 29 Set 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.
Risposta accettata
Walter Roberson
il 28 Set 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 Commenti
Fangjun Jiang
il 14 Apr 2023
t = num2cell([1,2,3,4]);
[a,b,c,d] = deal(t{:})
[a,b,c,d] = t{:}
Walter Roberson
il 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
Più risposte (4)
Raziman Thottungal Valapu
il 1 Ott 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 Commento
Stephen23
il 1 Ott 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
il 1 Set 2018
Modificato: Viktor
il 1 Set 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 Commenti
Daniel Birch
il 12 Set 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
il 12 Set 2018
Modificato: Stephen23
il 12 Set 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
il 14 Apr 2023
Modificato: Walter Roberson
il 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 Commenti
Fangjun Jiang
il 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
il 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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