Removing certain values from columns in a matrix

Hi!

I have a matrix looking something like this:

21 4.51076

21 48.3399

19 11.4743

21 36.6765

22 18.3587

23 19.7070

21 59.0842

20 40.9994

24 4.93227

28 44.4808

25 18.9996

24 29.4205

26 17.5263

26 28.4772

The elements in column 1 are as you can see not unique.

Out of the entrys in column 1 with the same value, i would like to keep only the smallest value in column 2 such as:

21 4.51076

NaN NaN

19 11.4743

Nan NaN

22 18.3587

23 19.7070

Nan NaN

20 40.9994

24 4.93227

28 44.4808

25 18.9996

NaN NaN

26 17.5263

NaN NaN

Any suggestions?

Regards,

Anders Holmberg

Answer 1

[Ameer Hamza]

Try this

A = [
    21	4.51076
    21	48.3399
    19	11.4743
    21	36.6765
    22	18.3587
    23	19.7070
    21	59.0842
    20	40.9994
    24	4.93227
    28	44.4808
    25	18.9996
    24	29.4205
    26	17.5263
    26	28.4772];

[~, idx] = sort(A(:,1));
C = splitapply(@(x) {[x(1,1) min(x(:,2)); nan(size(x)-[1 0])]}, A, findgroups(A(:,1)));
M = cell2mat(C);
M(idx,:) = M;

Result

>> M
M =
   21.0000    4.5108
       NaN       NaN
   19.0000   11.4743
       NaN       NaN
   22.0000   18.3587
   23.0000   19.7070
       NaN       NaN
   20.0000   40.9994
   24.0000    4.9323
   28.0000   44.4808
   25.0000   18.9996
       NaN       NaN
   26.0000   17.5263
       NaN       NaN

[Holmbrero]

That works perfectly! Thank you for the fast reply and solution.

Regards,

Anders Holmberg

[Ameer Hamza]

I am glad to be of help!