for 1:x with unkonw x

Question

Riccardo Rossi 2019-1-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438577-for-1-x-with-unkonw-x

评论： Riccardo Rossi 2019-1-7

采纳的回答： madhan ravi

Hi everybody,

i have an array like this:

ARRAY

X Y Z C

-3 4 5 1

5 6 2 2

4 4 9 1

6 6 7 2

4 6 2 3

9 9 7 3

where C goes from 1 to x (x unknow). I want to create a for to have x arrays with XYZ associated with C, like this:

for k=1:x

A(1:k)=[ARRAY(:,1),ARRAY(:,2),ARRAY(:,3),ARRAY(:,4)==1:k]

end

A1

X Y Z

-3 4 5

4 4 9

A2

X Y Z

5 6 2

6 6 7

A3

X Y Z

4 6 2

9 9 7

Thank you!

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Answer 1

madhan ravi 2019-1-7

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438577-for-1-x-with-unkonw-x#answer_355294

编辑：madhan ravi 2019-1-7

在 MATLAB Online 中打开

Don't think of naming variables dynamically (https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval ) use cell instead:

a=[-3  4  5  1
5  6  2   2
4  4  9   1
6  6  7   2
4  6  2   3
9  9  7   3];
u=unique(a(:,4));
A=cell(1,numel(u));
for i = 1:numel(u)
      idx = (a(:,4) == u(i)); % edited after Jan's comment
%     idx=ismember(a(:,4),u(i));
    A{i}=a(idx,1:3);
end
celldisp(A)

Gives:

A{1} =
 
    -3     4     5
     4     4     9
 
A{2} =
 
     5     6     2
     6     6     7
 
A{3} =
 
     4     6     2
     9     9     7

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madhan ravi 2019-1-7

编辑：madhan ravi 2019-1-7

在 MATLAB Online 中打开

Anytime :)

mean_of_X_Y_Z_in_each_cell=cellfun(@mean,A,'un',0)

Riccardo Rossi 2019-1-7

So grateful!

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Answer 2

KSSV 2019-1-7

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438577-for-1-x-with-unkonw-x#answer_355295

在 MATLAB Online 中打开

A = [-3  4  5  1
5  6  2   2
4  4  9   1
6  6  7   2
4  6  2   3
9  9  7   3 ] ;
C = A(:,end) ;
[c,ia,ib] = unique(C) ;
N = length(c) ;
iwant = cell(N,1) ;
for i = 1:N
    iwant{i} = A(C==c(i),1:3) ;
end