Assign Multiple Variables
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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 个评论
Image Analyst
2011-9-29
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.
采纳的回答
Walter Roberson
2011-9-28
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 个评论
Fangjun Jiang
2011-9-29
Or could work without deal. [a,b,c,d] = t{:}
Walter Roberson
2011-9-29
I don't believe I've see that documented. Based upon the descriptions of what {:} does, it would be reasonable to interpret it as equivalent to
[a,b,c,d] = t{1}, t{2}, t{3}, t{4}
which would be an invalid assignment (not enough output arguments) followed by three implicit disp()
Fangjun Jiang
2011-9-29
It is documented. See Example 3 at the bottom of this page.
http://www.mathworks.com/help/techdoc/ref/deal.html
Teja Muppirala
2011-9-29
编辑：Walter Roberson
2023-4-15
You COULD do it in one statement, but, you probably wouldn't want to...
X = [10 20 30 40];
[a,b,c,d] = subsref(num2cell(X),struct('type',{'{}'},'subs',{{1:4}}))
Edwin Fonkwe
2018-1-1
Hi Teja, I'm sorry if I sound rude, but this is a terrible implementation on Matlab!
Daniel Bridges
2018-1-25
Edwin, have you seen Mathematica? From the introductory documentation I've read, it seems Wolfram wants users to code like that from the beginning ...
t = num2cell([1,2,3,4]);
[a,b,c,d] = deal(t{:})
[a,b,c,d] = t{:}
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
更多回答（4 个）
Raziman Thottungal Valapu
2020-10-1
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 个评论
Stephen23
2020-10-1
@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.
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 个评论
Daniel Birch
2018-9-12
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
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
Jeff Miller
2018-8-15
3 个投票
matsplit does this.
Dan Erwin
2023-4-14
编辑：Walter Roberson
2023-4-14
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 个评论
Fangjun Jiang
2023-4-14
deal or no deal in MATLAB can do this already.
Fangjun Jiang
2023-4-14
@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
2023-4-15
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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