在 NumPy 中返回掩碼陣列的掩碼

要返回掩碼陣列的掩碼，請在 Python NumPy 中使用 **ma.getmask()** 方法。如果 a 是一個 MaskedArray 且掩碼不是 nomask，則返回 a 的掩碼作為 ndarray，否則返回 nomask。要保證與 a 形狀相同的布林值的完整陣列，請使用 getmaskarray。

掩碼陣列是標準 numpy.ndarray 和掩碼的組合。掩碼要麼是 nomask，表示關聯陣列的任何值均無效，要麼是布林值陣列，用於確定關聯陣列的每個元素的值是否有效。

步驟

首先，匯入所需的庫 -

import numpy as np
import numpy.ma as ma

使用 numpy.arange() 方法建立一個包含 int 元素的 4x4 陣列 -

arr = np.arange(16).reshape((4,4))
print("Array...
", arr)
print("
Array type...
", arr.dtype)

獲取陣列的維度 -

print("
Array Dimensions...
",arr.ndim)
print("
Our Array type...
", arr.dtype)

獲取陣列的形狀 -

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

獲取陣列的元素數量 -

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

建立一個掩碼陣列 -

arr = ma.array(arr)
arr[0, 1] = ma.masked
arr[1, 1] = ma.masked
arr[2, 1] = ma.masked
arr[2, 2] = ma.masked
arr[3, 0] = ma.masked
arr[3, 2] = ma.masked
arr[3, 3] = ma.masked

沿特定軸計算掩碼元素的數量 -

print("
The number of masked elements...
",ma.count_masked(arr, axis = 1))

要返回掩碼陣列的掩碼，請在 Python NumPy 中使用 ma.getmask() 方法 -

print("
Result (mask of a masked array)...
",ma.getmask(arr))

示例

import numpy as np
import numpy.ma as ma

# Creating a 4x4 array with int elements using the numpy.arange() method
arr = np.arange(16).reshape((4,4))
print("Array...
", arr)
print("
Array type...
", arr.dtype)

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

# Get the shape of the Array
print("
Our Masked Array Shape...
",arr.shape)

# Get the number of elements of the Array
print("
Elements in the Masked Array...
",arr.size)

# Create a masked array
arr = ma.array(arr)
arr[0, 1] = ma.masked
arr[1, 1] = ma.masked
arr[2, 1] = ma.masked
arr[2, 2] = ma.masked
arr[3, 0] = ma.masked
arr[3, 2] = ma.masked
arr[3, 3] = ma.masked

# Count the number of masked elements along specific axis
print("
The number of masked elements...
",ma.count_masked(arr, axis = 1))

# To return the mask of a masked array, use the ma.getmask() method in Python Numpy
print("
Result (mask of a masked array)...
",ma.getmask(arr))

輸出

Array...
[[ 0 1 2 3]
[ 4 5 6 7]
[ 8 9 10 11]
[12 13 14 15]]

Array type...
int64

Array Dimensions...
2

Our Array type...
int64

Our Masked Array Shape...
(4, 4)

Elements in the Masked Array...
16

The number of masked elements...
[1 1 2 3]

Result (mask of a masked array)...
[[False True False False]
[False True False False]
[False True True False]
[ True False True True]]

AmitDiwan

更新於: 2022年2月21日

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