Numpy recarray.compress() function | Python
Last Updated :
23 Apr, 2019
In numpy, arrays may have a data-types containing fields, analogous to columns in a spreadsheet. An example is [(a, int), (b, float)]
, where each entry in the array is a pair of (int, float). Normally, these attributes are accessed using dictionary lookups such as arr['a'] and arr['b']
.
Record arrays allow the fields to be accessed as members of the array, using arr.a and arr.b
. numpy.recarray.compress()
function return selected slices of an array along given axis.
Syntax : numpy.recarray.compress(condition, axis=None, out=None)
Parameters:
condition : [1-D array of bool] Array that selects which entries to return.
axis : [int, optional] Axis along which to take slices.
out : Results will be placed in this array.
Return : compressed_array, ndarray.
Code #1 :
import numpy as geek
in_arr = geek.array([[( 5.0 , 2 ), ( 3.0 , - 4 ), ( 6.0 , 9 )], [( 9.0 , 1 ), ( 5.0 , 4 ), ( - 12.0 , - 7 )]],
dtype = [( 'a' , float ), ( 'b' , int )])
print ( "Input array : " , in_arr)
rec_arr = in_arr.view(geek.recarray)
print ( "Record array of int: " , rec_arr.b)
float_rec_arr = rec_arr.a
print ( "Record array of float: " , float_rec_arr)
out_arr = (rec_arr.a).compress([ 0 , 1 ], axis = 0 )
print ( "Output compressed array : " , out_arr)
int_rec_arr = rec_arr.b
print ( "Record array of int: " , int_rec_arr)
out_arr = int_rec_arr.compress([ True , False ], axis = 1 )
print ( "Output compressed array : " , out_arr)
|
Output:
Input array : [[(5.0, 2) (3.0, -4) (6.0, 9)]
[(9.0, 1) (5.0, 4) (-12.0, -7)]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Record array of float: [[ 5. 3. 6.]
[ 9. 5. -12.]]
Output compressed array : [[ 9. 5. -12.]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Output compressed array : [[2]
[1]]
Code #2 :
import numpy as geek
in_arr = geek.array([[( 5.0 , 2 ), ( 3.0 , - 4 ), ( 6.0 , 9 )], [( 9.0 , 1 ), ( 5.0 , 4 ), ( - 12.0 , - 7 )]],
dtype = [( 'a' , float ), ( 'b' , int )])
print ( "Input array : " , in_arr)
rec_arr = in_arr.view(geek.recarray)
print ( "Record array of int: " , rec_arr.b)
out_arr = rec_arr.compress([ True , False ], axis = 1 )
print ( "Output compressed array : " , out_arr)
|
Output:
Input array : [[(5.0, 2) (3.0, -4) (6.0, 9)]
[(9.0, 1) (5.0, 4) (-12.0, -7)]]
Record array of int: [[ 2 -4 9]
[ 1 4 -7]]
Output compressed array : [[(5.0, 2)]
[(9.0, 1)]]
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