sortrows(data, [2,1]) is doing the 2nd round of sorting incorrectly in MATLAB R2017a

Here is some data I'm trying to sort by rows:

-80.0000    5.6250    1.0000
-45.0000    5.6250    1.0000
 45.0000    5.6250    1.0000
-65.0000    5.6250    1.0000
 25.0000    5.6250    1.0000
-40.0000    5.6250    1.0000
-25.0000    5.6250    1.0000
-15.0000    5.6250    1.0000
-10.0000    5.6250    1.0000
       0    5.6250    1.0000
 10.0000    5.6250    1.0000
 15.0000    5.6250    1.0000
 35.0000    5.6250    1.0000
-35.0000    5.6250    1.0000
-30.0000    5.6250    1.0000
-20.0000    5.6250    1.0000
 -5.0000    5.6250    1.0000
  5.0000    5.6250    1.0000
 20.0000    5.6250    1.0000
 40.0000    5.6250    1.0000
-55.0000    5.6250    1.0000
 30.0000    5.6250    1.0000
 55.0000    5.6250    1.0000
 65.0000    5.6250    1.0000
 80.0000    5.6250    1.0000

If I do

sortrows(data,1);

I get the following desired result:

-80.0000    5.6250    1.0000
-65.0000    5.6250    1.0000
-55.0000    5.6250    1.0000
-45.0000    5.6250    1.0000
-40.0000    5.6250    1.0000
-35.0000    5.6250    1.0000
-30.0000    5.6250    1.0000
-25.0000    5.6250    1.0000
-20.0000    5.6250    1.0000
-15.0000    5.6250    1.0000
-10.0000    5.6250    1.0000
 -5.0000    5.6250    1.0000
       0    5.6250    1.0000
  5.0000    5.6250    1.0000
 10.0000    5.6250    1.0000
 15.0000    5.6250    1.0000
 20.0000    5.6250    1.0000
 25.0000    5.6250    1.0000
 30.0000    5.6250    1.0000
 35.0000    5.6250    1.0000
 40.0000    5.6250    1.0000
 45.0000    5.6250    1.0000
 55.0000    5.6250    1.0000
 65.0000    5.6250    1.0000
 80.0000    5.6250    1.0000

However, if I do

sortrows(data,[2,1]);

I get the following wrong result:

-80.0000    5.6250    1.0000
-45.0000    5.6250    1.0000
 45.0000    5.6250    1.0000
-65.0000    5.6250    1.0000
 25.0000    5.6250    1.0000
-40.0000    5.6250    1.0000
-25.0000    5.6250    1.0000
-15.0000    5.6250    1.0000
-10.0000    5.6250    1.0000
       0    5.6250    1.0000
 10.0000    5.6250    1.0000
 15.0000    5.6250    1.0000
 35.0000    5.6250    1.0000
-35.0000    5.6250    1.0000
-30.0000    5.6250    1.0000
-20.0000    5.6250    1.0000
 -5.0000    5.6250    1.0000
  5.0000    5.6250    1.0000
 20.0000    5.6250    1.0000
 40.0000    5.6250    1.0000
-55.0000    5.6250    1.0000
 30.0000    5.6250    1.0000
 55.0000    5.6250    1.0000
 65.0000    5.6250    1.0000
 80.0000    5.6250    1.0000

Can someone please explain why this is happening? Just FYI, I need to use

sortrows(data,[2,1]);

in my code because the data I've shown here is part of a larger chunk where the values in the second column are different.

Answer 1

[srahulram]

Nevermind. It's a rounding issue. Doing

round(data,3);

first fixed it.

Answer 2

[Roger Stafford]

I would hazard the guess that in spite of their appearance using “format short” as you clearly have, the values in the second column are not really all equal. Based on the behavior you show, there are apparently at least five different values present there. Try doing an ‘fprintf’ with %22.20f on that second column and see if I am not right.

for k = 1:25
  fprintf(‘%22.20f\n’,data(k,2))
end

[srahulram]

Thanks! I was hasty to post. I should have known it's highly unlikely that something as basic as a sorting function could actually be wrongly programmed. Apologies!