How to create a matrix from for loop result?

Question

Hang Vu 2019-4-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458952-how-to-create-a-matrix-from-for-loop-result

评论： Hang Vu 2019-4-29

I repelem the element by the index

D = [170, -80, -30, 0, -50, -30, 20, -60, 100, -60 -20];
Iplus=find(D>0);
for i=1:size(Iplus,2)
    a=ceil(D(Iplus(i))/100);   
    A=repelem(Iplus(i),a*2)
end

How can I store all result as below into one matrix? like A=[1 1 1 1 7 7 9 9]

A =
     1     1     1     1
A =
     7     7
A =
     9     9

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Answer 1

Jos (10584) 2019-4-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458952-how-to-create-a-matrix-from-for-loop-result#answer_372629

在 MATLAB Online 中打开

D = [170, -80, -30, 0, -50, -30, 20, -60, 100, -60 -20];
Iplus=find(D>0);
A = [] ;           % initialize
for i=1:size(Iplus,2)
    a=ceil(D(Iplus(i))/100);   
    Anew = repelem(Iplus(i),a*2)
    A = [A Anew]   % append
end

Note that Matlab will warn you, because A is growing every iteration. With some thinking you might be able to optimise or even vectorise this piece of code.