[Python] NumPy – 2次元配列の対角線要素を取得する方法

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 主対角線要素の取得
diagonal_elements = np.diag(array_2d)
print(diagonal_elements)

[1 5 9]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 上側の対角線要素の取得
upper_diagonal = np.diag(array_2d, k=1)
print(upper_diagonal)
# 下側の対角線要素の取得
lower_diagonal = np.diag(array_2d, k=-1)
print(lower_diagonal)

[2 6]
[4 8]

import numpy as np
# 1次元配列の作成
array_1d = np.array([1, 2, 3])
# 対角行列の作成
diagonal_matrix = np.diag(array_1d)
print(diagonal_matrix)

[[1 0 0]
 [0 2 0]
 [0 0 3]]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[10, 20, 30],
                     [40, 50, 60],
                     [70, 80, 90]])
# 主対角線要素の取得
diagonal_elements = np.diag(array_2d)
print(diagonal_elements)

[10 50 90]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[10, 20, 30],
                     [40, 50, 60],
                     [70, 80, 90]])
# 上側の対角線要素の取得
upper_diagonal = np.diag(array_2d, k=1)
print("上側の対角線要素:", upper_diagonal)
# 下側の対角線要素の取得
lower_diagonal = np.diag(array_2d, k=-1)
print("下側の対角線要素:", lower_diagonal)

上側の対角線要素: [20 60]
下側の対角線要素: [40 80]

import numpy as np
# 1次元配列の作成
array_1d = np.array([5, 10, 15])
# 対角行列の作成
diagonal_matrix = np.diag(array_1d)
print(diagonal_matrix)

[[ 5  0  0]
 [ 0 10  0]
 [ 0  0 15]]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 主対角線要素の取得
diagonal_elements = np.diag(array_2d)
# 対角線要素の合計を計算
diagonal_sum = np.sum(diagonal_elements)
print("対角線要素の合計:", diagonal_sum)

対角線要素の合計: 15

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 対角線要素を10に変更
np.fill_diagonal(array_2d, 10)
print("変更後の配列:\n", array_2d)

変更後の配列:
 [[10  2  3]
 [ 4 10  6]
 [ 7  8 10]]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 対角線要素をゼロに変更
np.fill_diagonal(array_2d, 0)
print("対角線要素をゼロにした配列:\n", array_2d)

対角線要素をゼロにした配列:
 [[0 2 3]
 [4 0 6]
 [7 8 0]]

import numpy as np
# 1次元配列の作成
array_1d = np.array([1, 2, 3, 4])
# 対角行列の作成
diagonal_matrix = np.diag(array_1d)
print("対角行列:\n", diagonal_matrix)

対角行列:
 [[1 0 0 0]
 [0 2 0 0]
 [0 0 3 0]
 [0 0 0 4]]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 主対角線要素の合計を取得
diagonal_sum = np.trace(array_2d)
print("対角線要素の合計:", diagonal_sum)

対角線要素の合計: 15

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 主対角線要素を手動で取得
diagonal_elements = []
rows, cols = array_2d.shape
for i in range(min(rows, cols)):
    diagonal_elements.append(array_2d[i, i])
print("主対角線要素:", diagonal_elements)

主対角線要素: [np.int64(1), np.int64(5), np.int64(9)]

import numpy as np
# 2次元配列の作成
array_2d = np.array([[1, 2, 3],
                     [4, 5, 6],
                     [7, 8, 9]])
# 対角線要素を100に変更
np.fill_diagonal(array_2d, 100)
print("変更後の配列:\n", array_2d)

変更後の配列:
 [[100   2   3]
 [  4 100   6]
 [  7   8 100]]