# Create an array class with possibly masked values and fill in the masked values in Numpy

Create a masked array using the ma.MaskedArray() method. The mask is set using the "mask" parameter. Set to False here. The datatype is set using the "dtype" parameter. The fill_value parameter is used to fill in the masked values when necessary. A masked array is the combination of a standard numpy.ndarray and a mask. A mask is either nomask, indicating that no value of the associated array is invalid, or an array of booleans that determines for each element of the associated array whether the value is valid or not.

## Steps

At first, import the required library −

import numpy as np
import numpy.ma as ma

Create an array with int elements using the numpy.array() method −

arr = np.array([[77, 51, 92], [56, 31, 69], [73, 88, 51], [62, 45, 67]])
print("Array...", arr)
print("Array type...", arr.dtype)

Get the dimensions of the Array −

print("Array Dimensions...",arr.ndim)

Create a masked array. The mask is set using the "mask" parameter. Set to False here. The datatype is set using the "dtype" parameter. The fill_value parameter is used to fill in the masked values when necessary −

maskArr = ma.MaskedArray(arr, mask = [[1, 1, 0], [ 1, 0, 0], [0, 1, 0], [0, 1, 0]],
dtype=float, fill_value = 9999)
print("Our Masked Array type...", maskArr.dtype)

Get the dimensions of the Masked Array −

print("Our Masked Array Dimensions...",maskArr.ndim)

Get the shape of the Masked Array −

print("Our Masked Array Shape...",maskArr.shape)

Get the number of elements of the Masked Array −

print("Elements in the Masked Array...",maskArr.size)


Displaying the fill_value −

print("Result (fill value)...",maskArr.get_fill_value())

## Example

# Python ma.MaskedArray - Create an array class with possibly masked values and fill

import numpy as np
import numpy.ma as ma

# Create an array with int elements using the numpy.array() method
arr = np.array([[77, 51, 92], [56, 31, 69], [73, 88, 51], [62, 45, 67]])
print("Array...", arr)
print("Array type...", arr.dtype)

# Get the dimensions of the Array
print("Array Dimensions...",arr.ndim)

# The mask is set using the "mask" parameter. Set to False here
# The datatype is set using the "dtype" parameter
# The fill_value parameter is used to fill in the masked values when necessary
maskArr = ma.MaskedArray(arr, mask = [[1, 1, 0], [ 1, 0, 0], [0, 1, 0], [0, 1, 0]],
dtype=float, fill_value = 9999)

# Get the dimensions of the Masked Array

# Get the shape of the Masked Array

# Get the number of elements of the Masked Array

# Displaying the fill_value
print("Result (fill value)...",maskArr.get_fill_value())

## Output

Array...
[[77 51 92]
[56 31 69]
[73 88 51]
[62 45 67]]

Array type...
int64

Array Dimensions...
2

[[-- -- 92.0]
[-- 31.0 69.0]
[73.0 -- 51.0]
[62.0 -- 67.0]]

float64

2

(4, 3)

12
Result (fill value)...
9999.0

Updated on: 03-Feb-2022

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