Numpy MaskedArray.atleast_3d() function | Python

Last Updated : 13 Oct, 2019

numpy.MaskedArray.atleast_3d() function is used to convert inputs to masked arrays with at least three dimension.Scalar, 1-dimensional and 2-dimensional arrays are converted to 3-dimensional arrays, whilst higher-dimensional inputs are preserved.

Syntax : numpy.ma.atleast_3d(*arys) Parameters: arys:[ array_like] One or more input arrays. Return : [ ndarray] An array, or list of arrays, each with arr.ndim >= 3

Code #1 :

Python3

# Python program explaining
# numpy.MaskedArray.atleast_3d() method 
  
# importing numpy as geek  
# and numpy.ma module as ma 
import numpy as geek 
import numpy.ma as ma 
  
# creating input arrays  
in_arr1 = geek.array([ 3, -1, 5, -3])
print ("1st Input array : ", in_arr1)

in_arr2 = geek.array(2)
print ("2nd Input array : ", in_arr2)

in_arr3 = geek.array([[1, 2], [ 3, -1], [ 5, -3]])
print ("3rd Input array : ", in_arr3) 
  
# Now we are creating  masked array. 
# by making  entry as invalid.  
mask_arr1 = ma.masked_array(in_arr1, mask =[ 1, 0, 1, 0]) 
print ("1st Masked array : ", mask_arr1)

mask_arr2 = ma.masked_array(in_arr2, mask = 0) 
print ("2nd Masked array : ", mask_arr2)

mask_arr3 = ma.masked_array(in_arr3, mask =[[ 1, 0], [ 0, 1], [ 0, 0]]) 
print ("3rd Masked array : ", mask_arr3)
  
# applying MaskedArray.atleast_3d methods 
# to masked array 
out_arr = ma.atleast_2d(mask_arr1, mask_arr2, mask_arr3) 
print ("Output masked array : ", out_arr)

Output:

1st Input array :  [ 3 -1  5 -3]
2nd Input array :  2
3rd Input array :  [[ 1  2]
 [ 3 -1]
 [ 5 -3]]
1st Masked array :  [-- -1 -- -3]
2nd Masked array :  2
3rd Masked array :  [[-- 2]
 [3 --]
 [5 -3]]
Output masked array :  [masked_array(data=[[--, -1, --, -3]],
             mask=[[ True, False,  True, False]],
       fill_value=999999), masked_array(data=[[2]],
             mask=[[False]],
       fill_value=999999), masked_array(
  data=[[--, 2],
        [3, --],
        [5, -3]],
  mask=[[ True, False],
        [False,  True],
        [False, False]],
  fill_value=999999)]

Code #2 :

Python3

# Python program explaining
# numpy.MaskedArray.atleast_3d() method 
   
# importing numpy as geek  
# and numpy.ma module as ma 
import numpy as geek 
import numpy.ma as ma 
   
# creating input array 
in_arr = geek.array([[[ 2e8, 3e-5]], [[ -45.0, 2e5]]])
print ("Input array : ", in_arr)
    
# Now we are creating a masked array. 
# by making one entry as invalid.  
mask_arr = ma.masked_array(in_arr, mask =[[[ 1, 0]], [[ 0, 0]]]) 
print ("3D Masked array : ", mask_arr) 
   
# applying MaskedArray.atleast_3d methods 
# to masked array
out_arr = ma.atleast_3d(mask_arr) 
print ("Output masked array : ", out_arr)

Output:

Input array :  [[[ 2.0e+08  3.0e-05]]

 [[-4.5e+01  2.0e+05]]]
3D Masked array :  [[[-- 3e-05]]

 [[-45.0 200000.0]]]
Output masked array :  [[[-- 3e-05]]

 [[-45.0 200000.0]]]