Could anyone help me how to display the top three highest values in each column and display the other values to be zero.

I am having a matrix

A= [2.3433    2.8950    2.9967    3.8753    3.9190    3.9104    3.9563    3.9525;
    0.5167    0.4839    0.4885    0.1197    0.2249    0.2497    0.2874    0.2798;
    0.4429    0.4348    0.4009    0.2255    0.1793    0.2188    0.1807    0.1816;
    0.3900    0.1836    0.1741    0.1292    0.1241    0.1093    0.1058    0.1280;
    0.0792    0.1701    0.1765    0.1033    0.0859    0.0758    0.0681    0.0769;
    0.2301    0.1068    0.1036    0.0698    0.0868    0.0945    0.0912    0.0847]

I want to display the top three highest values in each column and the rest of the other values should be displayed as zero.

Could anyone please help me on this.

Answer 1

[Guillaume]

Getting the top 3 values of each column is trivial with maxk

top3 = maxk(A, 3, 1)

I don't see the point in having 0s below these values but if that's you really want, you can simply concatenate a zero matrix below that

top3padded = [mask(A, 3, 1); zeros(size(A, 1)-3, size(A, 2))]

[jaah navi]

When i use the above command its staing undefined function or variable maxk,mask.

For your info if

   A=[0.5238    0.9547    0.7060    0.3709    0.9102    0.9044    0.1877    0.2748;
      0.2649    0.4306    0.6451    0.8909    0.9091    0.0332    0.3219    0.2415;
      0.0684    0.9616    0.5523    0.8564    0.5916    0.5324    0.4039    0.2431;
      0.4363    0.7624    0.2181    0.4024    0.3326    0.7165    0.5486    0.1542;
      0.1739    0.0073    0.7724    0.3180    0.8531    0.1793    0.0487    0.9564;
      0.0261    0.6800    0.2280    0.6086    0.4424    0.3365    0.5527    0.9357]

i need to have

 B=[0.5238    0.9547    0.7060    0         0.9102    0.9044    0         0.2748;
    0.2649    0         0.6451    0.8909    0.9091    0         0         0     ;
    0         0.9616    0         0.8564    0         0.5324    0.4039    0     ;
    0.4363    0.7624    0         0         0         0.7165    0.5486    0     ;
    0         0         0.7724    0         0.8531    0         0         0.9564;
    0         0         0         0.6086    0         0         0.5527    0.9357]

Could you please help me on this.

[Guillaume]

You're probably on a version earlier than 2017b. Please fill the release field on the top right of the page.

On old versions, you'll have to use sort as shown by Geoff.

edit: Actually looking at your desired output, it's slightly more complicated:

[~, roworder] = sort(A, 1, 'descend');
A(sub2ind(size(A), roworder(4:end, :), repmat(1:size(A, 2), size(A, 1)-3, 1))) = 0

Answer 2

[Geoff Hayes]

jaah - try using sort to sort the columns of your matrix in descending order

B = sort(A, 'descend');

To set all but the first three columns to zero, then do

B(4:end,:) = 0;