Replace double numbers in a matrix with new ones

Question

Susu 2023-8-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2005202-replace-double-numbers-in-a-matrix-with-new-ones

评论： Walter Roberson 2023-8-7

How can I ensure that 2 matrices have numbers from 1 to 40. BUT the columns of the two matrices are different, so that the numbers that appear in the first matrix may not appear in the second matrix in the first column.

Therefore, I can check whether a number that is in the 1st column of the 1st matrix is also in the 1st column of the 2nd matrix and if this is the case, then this number (from the 1st column of the 2nd matrix) should be assigned another number that is not in the 1st column of the 1st matrix.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2023-8-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2005202-replace-double-numbers-in-a-matrix-with-new-ones#answer_1283932

在 MATLAB Online 中打开

found = ismember(SecondMatrix(:,1), FirstMatrix(:,1));

now reassign Secondmatrix(found, 1)

... or, you know, you could do

temp = randperm(40);
FirstMatrix(:,1) = temp(1:20);
SecondMatrix(:,1) = temp(21:40);

Guaranteed that afterwards, no entry in SecondMatrix(:,1) appears in FirstMatrix(:,1)

11 个评论
显示 9更早的评论隐藏 9更早的评论

Susu 2023-8-6

在 MATLAB Online 中打开

My mistake, I did not express myself correctly.

It is true that this above procedure causes the numbers in the columns to vary, however. My matrices are constructed as follows:

FirstMatrix=reshape(randperm(40),4,10); SecondMatrix=reshape(randperm(40),4,10);

Therefore, I do not want the column contents to appear again in the same form in the other matrix. I do not want the number assignments from the first matrix to reappear in the second.

So the numbers of the 1st column of the 1st matrix should not appear 1:1 (regardless of the order) in the 2nd matrix.

Therefore, I would like to mix the numbers and only then divide them, but my only condition is that if the number was already in the 5th column in the previous matrix, then it should not appear again in the 5th column in the current matrix.

E.g. Starting from my matrices above

I get something like this:

In this case I don't want the numbers 15,26,4 and 17 from the 3rd column to appear in the 2nd matrix in the 3rd column and basically no other column is filled with these numbers (because then the column would be filled with the same numbers as in one and I don't want that, even if the order varies).

In this example, none of the 3rd column of the 1st matrix is in the 3rd column of the 2nd matrix, so it fits.

Only what does not fit is the number 31 in the 2nd column of the 2nd matrix and the number 12 in the 5th column of the 2nd matrix. Because these already appear in the columns of the previous matrix.

I hope it is now easier to understand. Many thanks already :)

FirstMatrix=reshape(randperm(40),4,10)
FirstMatrix = 4×10
     9    18    15     3    39    24    19    35    13     5
     7    14    26    27    23     8    20    25    28    16
    21    31     4     6    12    37    36    10     1    11
    38    33    17    29     2    30    32    34    22    40
SecondMatrix=reshape(randperm(40),4,10)
SecondMatrix = 4×10
    20    38    23     9     6    15    35    32    24     2
     1    16    22    21    12    19     3    26    37    28
    40    31    36    25     5    13    27     4    33    34
     7    17    10    30    29    39    18    11    14     8

Walter Roberson 2023-8-6

在 MATLAB Online 中打开

T1 = 1 : 40;
T2 = randperm(numel(T1),4)
T2 = 1×4
    36    33    37     9
T1(T2) = [];
T3 = reshape(T1(randperm(numel(T1))), 4, [])
T3 = 4×9
    20    17    16     7    31    28    18    11    26
     1    15    13     4     3    35    39    34     8
    30    19     5    40     2    21    29    12    24
    38    27    22    14    25    10    32     6    23
output = [T2(:), T3]
output = 4×10
    36    20    17    16     7    31    28    18    11    26
    33     1    15    13     4     3    35    39    34     8
    37    30    19     5    40     2    21    29    12    24
     9    38    27    22    14    25    10    32     6    23

I don't know exactly how to filter for the number that appears in the same columns of the two matrices

My very first response was to show you how to use ismember() to do the filtering.

What I have been pointing out since then is that you can avoid that by strategic use of randperm and indexing. Pay attention to the way T3 was constructed: T1(T2) = []; on the line above removes from T1 all of the elements that were already used, and T1(randperm(numel(T1))) is then a random re-ordering of everything that is left over.

Image Analyst 2023-8-7

What is the use case? WHY do you want this thing? Is it homework, or is there some real world need for it?

Walter Roberson 2023-8-7

在 MATLAB Online 中打开

found = ismember(SecondMatrix(:,1), FirstMatrix(:,1));
SecondMatrix(found,1) = 0;
candidates = setdiff(1:40, SecondMatrix(:,1));
SecondMatrix(found,1) = candidates(randperm(numel(candidates), sum(found)));

请先登录，再进行评论。