Sorting an 3-dimensional array by a single row/column in Python

Question

m,n) shaped numpy array. I would like to sort the whole array by the values in the index [1,2,:] say. Is there an easy way to do this? I tried to use pandas Panel but for whatever reason there is no sort by values function for it.

That 'duplicate' someone linked only seems to work for a column in an 2d array. I am using the term column in a more general sense i.e a 1d sub-array of an (mxnxlx..) array

Possible duplicate of How to sort multidimensional array by column? — jHilscher
– jHilscher, Commented Aug 22, 2016 at 18:05
Use argsort on the selected row/column, and then order the array with that index. — hpaulj
– hpaulj, Commented Aug 22, 2016 at 18:39

shaun252 · Accepted Answer · 2016-08-23 10:50:03Z

0

So how I did it was using argsort as hpaulj said, given a array arr that was (m,n,l) dimension and a column indexed by (i,j,:).

sorted = np.empty(arr.shape):
for k in range(arr.shape[2]):
    sorted[:,:,i] = arr[:,:,np.argsort(arr[i,j,:])[i]]

answered Aug 23, 2016 at 10:50

shaun252

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