How to create groups by using labels?

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Jim
Jim 2019-10-4
评论： Daniel M 2019-10-8
I have two arrays, one with values and one with labels, both of the same length.
For example :
V = [ 1 2 3 4 5 6 7 8]
L = { 'A', 'A', 'A', 'C', 'C', 'C', 'A', 'B' }
now I want to use to labels to split V into three groups like:
A = [1 2 3 7]
B = [8]
C = [4 5 6]
How do I do that? Cant find it anywhere

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采纳的回答

the cyclist
the cyclist 2019-10-4
Here is one way:
V = [ 1 2 3 4 5 6 7 8];
L = { 'A', 'A', 'A', 'C', 'C', 'C', 'A', 'B' };
[tf,loc] = ismember(L,unique(L));
for ni = 1:max(loc)
VV{ni} = V(loc==ni)
end
Note that I used a cell array to store the output, rather than the alphabetic sequence variables.

更多回答（1 个）

Daniel M
Daniel M 2019-10-4
编辑：Daniel M 2019-10-4
I don't recommend making variables dynamically for various reasons, but making a struct is fine to do, and can even make fieldnames dynamically:
[uL,~,iL] = unique(L);
for f = 1:length(uL)
s.(uL{f}) = V(iL==f);
end
The output struct s will have fieldnames that are the same as the labels in L.
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Jim
Jim 2019-10-8
This doesnt work if the labels are numbers.
Do you have any idea how to make it work for numberlabels aswell?
Daniel M
Daniel M 2019-10-8
Well, how would you have done it manually? In your original post you wanted to make variables named A = [1 2 3 7], etc. How would you have done it if the label was a number instead?
You can try prepending a letter before any labels that start with numbers.
L = {'A','A','B','2','C','1','x1','1x'}
s = ~cellfun(@isempty, regexp(L,'^\d'),'UniformOutput',true) % finds the labels that start with a number
L(s) = cellfun(@(x) ['n',x],L(s),'UniformOutput',false); % preprend with the letter n
L
with output
L =
1×8 cell array
{'A'} {'A'} {'B'} {'2'} {'C'} {'1'} {'x1'} {'1x'}
s =
1×8 logical array
0 0 0 1 0 1 0 1
L =
1×8 cell array
{'A'} {'A'} {'B'} {'n2'} {'C'} {'n1'} {'x1'} {'n1x'}

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