how to select higher value in a matrix and change that by introducing an error?

Question

suchismita 2014-6-2

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https://ww2.mathworks.cn/matlabcentral/answers/132055-how-to-select-higher-value-in-a-matrix-and-change-that-by-introducing-an-error

回答： suchismita 2014-6-2

采纳的回答： George Papazafeiropoulos

I have a matrix,

a= [ 0.83 0.85 0.97 0.1 0.95 0.93 0.2 ; 0.2 0.12 0.12 0.76 0.77 0.78 0.25 ; 0.88 0.32 0.11 0.77 0.87 0.89 0.99]

by ceil(a) we get c matrix: c=[ 1 1 1 0 1 1 0 ; 0 0 0 1 1 1 0 ; 1 0 0 1 1 1 1]

now i want to introduce error position wise as err=1:3

so, at first err=1 will be introduced to first row where the only highest value is find in matrix a and 1 will become 0,same wise in 2nd row and 3rd row. Then err=2, that means the first two highest value is find and 1 will become zero, then same will be carried out for 2nd,3rd row. Next err=3...where 3 higher value will be changed.

please help me out asap....

plz plz plz.....

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suchismita 2014-6-2

in sort() the position of matrix is changing...i want to identify the positions so that i can convert 1 to 0

Roger Wohlwend 2014-6-2

Yes, but the sort command also tells you the original position of the sorted values (it's the second output variable). Use that information.

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Answer 1

George Papazafeiropoulos 2014-6-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/132055-how-to-select-higher-value-in-a-matrix-and-change-that-by-introducing-an-error#answer_139161

在 MATLAB Online 中打开

Are you looking for something like this?

a= [ 0.83 0.85 0.97 0.1 0.95 0.93 0.2;
    0.2 0.12 0.12 0.76 0.77 0.78 0.25;
    0.88 0.32 0.11 0.77 0.87 0.89 0.99];
c=round(a)
for i=1:3
    for err=1:3
        [~,d]=sort(a(err,:),'descend');
        a(err,d(1:i))=0;
    end
end
cfinal=round(a)

I hope this will help!

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suchismita 2014-6-2

sort is changing the 'a' matrix itself....but i dont want to disturb a matrix, the changes i want to make in c....as in matrix a in first row 0.97 is highest so that value in c will become zero same wise in 2nd row 0.77 (a(2,5)) will become zero, same process will be carried in 3rd row. In second round, first row will take the two highest numbers as 0.97 (1,3)and next highest to it is 0.95 (1,5) will become zero.... this is the concept....plz help me....

George Papazafeiropoulos 2014-6-2

在 MATLAB Online 中打开

I think the following applies if you want the a matrix unaltered. The outer for loop (for i=1:3) is not required in this case, because for all i (=1,2,3) the maximum element of each row of A is selected and set to zero, so we can set i=3, select the three highest values, set them to zero and get rid of the initial i loop:

a= [ 0.83 0.85 0.97 0.1 0.95 0.93 0.2;
    0.2 0.12 0.12 0.76 0.77 0.78 0.25;
    0.88 0.32 0.11 0.77 0.87 0.89 0.99];
c=round(a)
for err=1:3
    [~,d]=sort(a(err,:),'descend');
    c(err,d(1:3))=0;
end