Is there Python equivalent to MATLAB unique?

Question

I am rewriting one code

nd = unique(nd,'rows');

Documentation from The Mathworks

C = unique(A,'rows') treats each row of A as a single entity and returns the unique rows of A. The rows of the array C are in sorted order.

Is there something like this in Python or I have to use sort?

if nd is a list of tuples you can just use `sorted(set(nd))` I guess ... if its lists then that will break since lists are mutable they cannot be hashed... — Joran Beasley, Mar 17 '16 at 18:11
lol np.unique is probably the right answer :P I figured np had something — Joran Beasley, Mar 17 '16 at 18:13
I second that. If you're migrating MATLAB code, you should be using numpy anyway. — Andras Deak -- Слава Україні, Mar 17 '16 at 18:13

score 3 · Accepted Answer · answered Mar 17 '16 at 18:16

3

import numpy as np

# Having an array:
a = [1,2,2,3,4,4,3]
print ("Original vector:")
print(a)

# Printting unique values of a:
print ("Unique values of a:")
print (np.unique(a))

# Other option:
print  ("Another way:")
print (set(a))

Ouput:

Original vector:
[1, 2, 2, 3, 4, 4, 3]
Unique values of a:
[1 2 3 4]
Another way:
{1, 2, 3, 4}

answered Mar 17 '16 at 18:16

Hugo Reyes

1,555
2
12
21

The MATLAB `unique` with 'rows' specified finds the unique *rows*. `np.unique` will return the unique elements from the flattened array. For 2D arrays see https://stackoverflow.com/questions/16970982/find-unique-rows-in-numpy-array – Klimaat Mar 22 '17 at 19:48

score 0 · Answer 2 · answered May 20 '20 at 03:56

Python:

a = np.array([[1, 0, 0], [1, 0, 0], [2, 3, 4], [2, 3, 4],[2, 3, 5],[1, 0, 0],[2,2,5],[2,3,5]])
c, ia, ic= np.unique(a,return_index=True,return_inverse=True, axis=0)

This will give the same result as the unique function of Matlab. The only difference is the base index which starts from 0 in Python.

Is there Python equivalent to MATLAB unique?

2 Answers2