Find the union of two NumPy arrays
To find union of two 1-dimensional arrays we can use function numpy.union1d() of Python Numpy library. It returns unique, sorted array with values that are in either of the two input arrays.
Syntax:
numpy.union1d(array1, array2)
Note The arrays given in input are flattened if they are not 1-dimensional.
Let’s see examples of how to find union of two arrays.
Example 1:
import numpy as np
arr1 = np.array([ 10 , 20 , 30 , 40 ])
print ( "array1 " , arr1)
arr2 = np.array([ 20 , 40 , 60 , 80 ])
print ( "array2 " , arr2)
print ( "Union of two arrays :" , np.union1d(arr1, arr2))
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Output:
Example 2:
Let’s see example of finding union of a 2-d and a 1-d array. As discussed earlier, if array passed as arguments to function numpy.union1d is 2-dimensional, then they are flattened to 1-dimension.
import numpy as np
arr1 = np.array([[ 1 , 2 , 3 ], [ 4 , 5 , 6 ]])
print ( "array1 " )
print (arr1)
arr2 = np.array([ 0 , 5 , 10 ])
print ( "array2 " , arr2)
print ( "Union of two arrays" , np.union1d(arr1, arr2))
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Output:
Example3:
If we want to find union of more than two arrays, then we can find that by using functools.reduce function.
import numpy as np
from functools import reduce
array = reduce (np.union1d, ([ 1 , 2 , 3 ], [ 1 , 3 , 5 ],
[ 2 , 4 , 6 ], [ 0 , 0 , 0 ]))
print ( "Union " , array)
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Output:
Last Updated :
05 Sep, 2020
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