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

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suchismita on 2 Jun 2014
Answered: suchismita on 2 Jun 2014
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.
plz plz plz.....
Roger Wohlwend on 2 Jun 2014
Yes, but the sort command also tells you the original position of the sorted values (it's the second output variable). Use that information.

George Papazafeiropoulos on 2 Jun 2014
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!
George Papazafeiropoulos on 2 Jun 2014
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

suchismita on 2 Jun 2014
thank u so much....ya i got it now....thank u so so so much...