Python 提取NumPy数组中具有最大和的n列

假设我有一个100行1000列的NumPy矩阵

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如何获得由原始矩阵中具有最高和的n列组成的新矩阵？

您可以使用@NPE所做的

np.argsort

。以下是两个较小阵列的示例：

def nlargest_cols(a, n):
    return a[:, sorted(a.sum(axis=0).argsort()[-n:][::-1])]

# `a` is a 3x4 array with column sums getting
#     larger from left to right.
a = np.arange(12).reshape(3,4)

# `b` is `a` rotated 2 turns.
b = np.rot90(a, 2)

print(nlargest_cols(a, 2))
# [[ 2  3]
#  [ 6  7]
#  [10 11]]

print(nlargest_cols(b, 3))
# [[11 10  9]
#  [ 7  6  5]
#  [ 3  2  1]]

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您可以像@NPE一样使用

np.argsort

。以下是两个较小阵列的示例：

def nlargest_cols(a, n):
    return a[:, sorted(a.sum(axis=0).argsort()[-n:][::-1])]

# `a` is a 3x4 array with column sums getting
#     larger from left to right.
a = np.arange(12).reshape(3,4)

# `b` is `a` rotated 2 turns.
b = np.rot90(a, 2)

print(nlargest_cols(a, 2))
# [[ 2  3]
#  [ 6  7]
#  [10 11]]

print(nlargest_cols(b, 3))
# [[11 10  9]
#  [ 7  6  5]
#  [ 3  2  1]]