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pythonarraysnumpy
Carlos Carvajal
Carlos Carvajal

Reputation: 11

Mapping row values to other values in the same numpy array

If I have a numpy array with objects such as the following: 

array(['Ana', 'Charlie', 'Andrew'], dtype=object)

And I want to map each object to all objects in the array so I obtain the following output:

array(['Ana', 'Ana'],['Ana','Charlie'],['Ana', 'Andrew'], 
['Charlie','ana'], ['Charlie','Charlie'],['Charlie','Andrew'], ['Andrew','ana'],['Andrew', 'Charlie'], ['Andrew','Andrew'], dtype=object).

how can I use numpy to map each object to all objects in the same array?

Thanks so much.

Upvotes: 0

Views: 169

Answers (3)

Fei Yao
Fei Yao

Reputation: 1742

The following code taking advantage of list comprehension should work fine.

import numpy as np
a=np.array(['Ana', 'Charlie', 'Andrew'], dtype=object)
b=np.array([[i,j] for i in a for j in a], dtype=object)

Upvotes: 0

yatu
yatu

Reputation: 88236

Python lists are generally more suited when dealing with strings. Looks like you want the cartesian product:

from itertools import product
l = ['Ana', 'Charlie', 'Andrew']

list(map(list, product(l,l)))

[['Ana', 'Ana'],
 ['Ana', 'Charlie'],
 ['Ana', 'Andrew'],
 ['Charlie', 'Ana'],
 ['Charlie', 'Charlie'],
 ['Charlie', 'Andrew'],
 ['Andrew', 'Ana'],
 ['Andrew', 'Charlie'],
 ['Andrew', 'Andrew']]

Upvotes: 1

Lone Lunatic
Lone Lunatic

Reputation: 835

You are searching for the cartesian product of the two arrays.

numpy.transpose() should do the trick:

x = array(['Ana', 'Charlie', 'Andrew'], dtype=object)
numpy.transpose([numpy.tile(x, len(x)), numpy.repeat(x, len(x))])

Upvotes: 1

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