Keep track of Matrix row indices after deleting some rows

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Nadatimuj on 18 Apr 2021
Commented: Nadatimuj on 18 Apr 2021
Suppose, I have a 10x10 Martix A= magic(10).
Then I delete some rows from it as A([3 5 6],:)=[]. and some columns as A(:,[3 5 6])=[]
Now it's a 7x7 matrix.
I want to keep track of the indices to know which row in the orginal matrix becomes which row in the transformed matrix.
A= magic(10);
A([3 5 6],:)=[];
A(:,[3 5 6])=[];
I want to keep track that previous 4th row is now the 3rd row...previous 7th row is now the 4th row...etc. Any solid way to do that? Please help. Thanks.

Answers (1)

KALYAN ACHARJYA on 18 Apr 2021
Edited: KALYAN ACHARJYA on 18 Apr 2021
You can store the A in a temporary variable, and do the modification on temp
Now do the all modification on temp. Result A is original and temp is the modified matrix. Afterwards you can do the comparision between A and temp, like simmilarity
  1 Comment
Nadatimuj on 18 Apr 2021
Thanks for your suggestion. I actually seek help for that "comparison" part. I need to save (for further use) a mapping of new indices that can give me the corresponding old index Matrix row
for example, temp(7,:) and modified(4,:) will give me similar row...I need such index mapping. Thanks.

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