`numpy.ma.core:MaskedArray.compressed`

Signature

def compressed(self)

Return all the non-masked data as a 1-D array.

The result is not a MaskedArray!

import numpy as np
x = np.ma.array(np.arange(5), mask=[0]*2 + [1]*3)
x.compressed()
type(x.compressed())

N-D arrays are compressed to 1-D.

arr = [[1, 2], [3, 4]]
mask = [[1, 0], [0, 1]]
x = np.ma.array(arr, mask=mask)
x.compressed()