How can I rearrange the order of elements in a string given a matrix with positions?

Question

Keanu Guardiola Flores 2018-2-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/380907-how-can-i-rearrange-the-order-of-elements-in-a-string-given-a-matrix-with-positions

回答： Voss 2023-12-20

I have a string array of the form: str =["e1","e5", "e7", "e3"] %there are 16 e's in total

I want to take that str and order it such that I get a matrix of the form: M = [ e1 e5 e9 e13; e2 e6 e10 e14; e3 e7 e11 e15; e4 e8 e12 e16]

and then rearrange the matrix with the positions such that I get them ordered like in matrix l.

To do that I wrote:

for i=1:16

    if ismember(sprintf('e%d',i), v)
         Order(i) =  sprintf('e%d',i);
         else
          Order(i)= sprintf('e%d',i);
    end
    [tf,loc] = ismember(sprintf('e%d',i),v);
    Positions(i) = loc;
l = [1 5 2 6;...
     9 13 10 14;...
     3 7 4 8;...
     11 15 12 16];
New_order = Positions(l);

In this example New_order = [1 2 0 0; 0 0 0 0; 4 3 0 0; 0 0 0 0]

Now, the problem is I have another vector b that is the same length as v: b = ( 1 5 7 3); and I want to create a matrix with its elements in the form of New_order, but if I try b(New_order) it won't allow me to do so because New_order contains zeros. How can I rearrange my vector b using New_order such that the output is: [1 5 0 0; 0 0 0 0; 3 7 0 0; 0 0 0 0] ?

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Answer 1

Voss 2023-12-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/380907-how-can-i-rearrange-the-order-of-elements-in-a-string-given-a-matrix-with-positions#answer_1375142

在 MATLAB Online 中打开

v = ["e1","e5","e7","e3"];
% these two lines replace your existing loop:
Order = compose("e%d",1:16);
[~,Positions] = ismember(Order,v);
l = [1 5 2 6;...
     9 13 10 14;...
     3 7 4 8;...
     11 15 12 16];
New_order = Positions(l)
New_order = 4×4
     1     2     0     0
     0     0     0     0
     4     3     0     0
     0     0     0     0
% now do the thing with b:
b = [1 5 7 3];
New_b = zeros(size(New_order));
idx = New_order ~= 0;
New_b(idx) = b(New_order(idx))
New_b = 4×4
     1     5     0     0
     0     0     0     0
     3     7     0     0
     0     0     0     0