[Matrix-SIG] Sorting arrays lexicographically by row

[jhauser@ifm.uni-kiel.de]

There is argsort, with which one can try to build a custom
sort-function.

But the most easy and probably also efficient method is to use pythons 
list sort.

The conversion from an array to a list of lists cost nearly no
time. The sorting on lists is definetly very good optimized.
So use:
>>> a
array([[3, 1],
       [3, 0],
       [2, 1],
       [1, 0],
       [2, 2]])
>>> b=a.tolist()
>>> b.sort()
>>> array(b)
array([[1, 0],
       [2, 1],
       [2, 2],
       [3, 0],
       [3, 1]])

The steps in between are needed, because the methods do not return
arrays. 

HTH,
__Janko

Edward C. Jones writes:
 > Here is a small piece of Python code:
 > 
 > arr = [[3,1], [3,0], [2,1], [1,0], [2,2]]
 > arr.sort()
 > print arr
 > 
 > The output is:
 > 
 > [[1, 0], [2, 1], [2, 2], [3, 0], [3, 1]]
 > 
 > Can I do this (lexicographic) type of sorting using NumPy on a
 > NumPy array?
 > 
 > Thanks,
 >   Ed Jones
 > 
 > 
 > 
 > _______________________________________________
 > Matrix-SIG maillist  -  Matrix-SIG@python.org
 > http://www.python.org/mailman/listinfo/matrix-sig
 >