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up vote 0 down vote favorite

I'am using numpy and have an array (ndarray type) which contain some values. Shape of this array 1000x1500. I reshaped it 

brr = np.reshape(arr, arr.shape[0]*arr.shape[1])

when I trying 

brr.reverse()
AttributeError: ‘numpy.ndarray’ object has no attribute ‘reverse’

get error. How I can sort this array ?

share|improve this question
    
sort or reverse? –  Rohit Jain Feb 14 '13 at 12:52
    
what are you expecting reverse() to do? –  NPE Feb 14 '13 at 12:52
    
Doesn't solve your problem, but to make your code a little neater and more efficient you can use arr.size instead of arr.shape[0]*arr.shape[1]. –  Junuxx Feb 14 '13 at 12:59
    
I want to sort it descending. Btw sort() give the same error –  user2046488 Feb 14 '13 at 13:12

2 Answers 2

up vote 5 down vote accepted

If you just want to reverse it:

brr[:] = brr[::-1]

Actually, this reverses along axis 0. You could also revert on any other axis, if the array has more than one.

To sort in reverse order:

>>> arr = np.random.random((1000,1500))
>>> brr = np.reshape(arr, arr.shape[0]*arr.shape[1])
>>> brr.sort()
>>> brr = brr[::-1]
>>> brr
array([  9.99999960e-01,   9.99998167e-01,   9.99998114e-01, ...,
     3.79672182e-07,   3.23871190e-07,   8.34517810e-08])

or, using argsort:

>>> arr = np.random.random((1000,1500))
>>> brr = np.reshape(arr, arr.shape[0]*arr.shape[1])
>>> sort_indices = np.argsort(brr)[::-1]
>>> brr[:] = brr[sort_indices]
>>> brr
array([  9.99999849e-01,   9.99998950e-01,   9.99998762e-01, ...,
         1.16993050e-06,   1.68760770e-07,   6.58422260e-08])
share|improve this answer
    
No, it is unsorted, I have to sort it descending –  user2046488 Feb 14 '13 at 13:10
    
Thanks! Tried argsort() with no luck. Did not knew about [::-1] –  user2046488 Feb 14 '13 at 13:36
up vote 0 down vote

Try this for sorting in descending order , 

import numpy as np
a = np.array([1,3,4,5,6])
print -np.sort(-a)
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