Find repeated values of one column and assign the lowest value from the group of second columns

Hello, say I have the following matrix:

12709.2240000000 -1.23920000000000

12709.2240000000 -1.23530000000000

12780.2225000000 -1.23530000000000

12617.2233000000 -1.23530000000000

12564.2233000000 -1.23530000000000

12512.2233000000 -1.23530000000000

12709.2240000000 -1.23390000000000

12780.2225000000 -1.23090000000000

And I wanted to remove duplicate rows by looking at the 1st column, but assign the lowest value from the group of duplicated values to the 2nd column. So that I get the following:

12709.2240000000 -1.23920000000000

12780.2225000000 -1.23530000000000

12617.2233000000 -1.23530000000000

12564.2233000000 -1.23530000000000

12512.2233000000 -1.23530000000000

So in this case for example, I have 3 rows with 12709.224 on the 1st column, and assign -1.2392 to the 2nd column which is the lowest value from -1.2392, -1.2353, -1.2339.

I think a way to do this would be to find the index position of equal values on the 1st column and then compare the values of the 2nd column with this index position and assign these onto a new matrix, is there a better way / optimized to do this?

Thank you.

Answer 1

[Voss]

M = [12709.2240000000 	-1.23920000000000
    12709.2240000000 	-1.23530000000000
    12780.2225000000 	-1.23530000000000
    12617.2233000000 	-1.23530000000000
    12564.2233000000 	-1.23530000000000
    12512.2233000000 	-1.23530000000000
    12709.2240000000 	-1.23390000000000
    12780.2225000000 	-1.23090000000000];

[gid,~,g] = unique(M(:,1),'stable');
minM2 = splitapply(@min,M(:,2),g);
M_new = [gid,minM2];

format longG
disp(M_new);

                 12709.224                   -1.2392
                12780.2225                   -1.2353
                12617.2233                   -1.2353
                12564.2233                   -1.2353
                12512.2233                   -1.2353

[JIAN-HONG YE ZHU]

Thank you very much

[Voss]

You're welcome!