python数据分析与机器学习实战-02.Numpy基础结构

import numpy
#数据运算
vector = numpy.array([3,6,7,89,90])
vector == 6

1	array([False, True, False, False, False])

1	matrix = numpy.array([[12,3,67,9],[34,2,7,9],[3,8,9,6]])matrix == 3

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array([[False,  True, False, False],
       [False, False, False, False],
       [ True, False, False, False]])

vector = numpy.array([3,6,7,89,90])
equal_to_six = (vector == 6)
print(equal_to_six)
print(vector[equal_to_six])

1 2	[False True False False False] [6]

matrix = numpy.array([[12,3,67,9],[34,2,7,9],[3,8,9,6]])
second_column_three = (matrix[:,1] == 3)
print(second_column_three)
print(matrix[second_column_three,:])

1 2	[ True False False] [[12 3 67 9]]

#逻辑运算
vector = numpy.array([3,6,7,89,90])
equal_to_three_and_six = (vector == 3)&(vector == 6)
print(equal_to_three_and_six)

1	[False False False False False]

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vector = numpy.array([3,6,7,89,90])
equal_to_three_or_six = (vector == 3)|(vector == 6)
print(equal_to_three_or_six)

1	[ True True False False False]

1	#类型转换vector = numpy.array(['3','6','7','89','90'])print(vector.dtype)vector = vector.astype(float)print(vector.dtype)print(vector)

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<U2
float64
[ 3.  6.  7. 89. 90.]

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#最小值
vector = numpy.array([3,6,7,89,90])
print(vector.min())

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#最大值
vector = numpy.array([3,6,7,89,90])
print(vector.max())

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#列求和
matrix = numpy.array([[12,3,67,9],[34,2,7,9],[3,8,9,6]])
print(matrix.sum(axis=0))

1	[49 13 83 24]

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#行求和
matrix = numpy.array([[12,3,67,9],[34,2,7,9],[3,8,9,6]])
print(matrix.sum(axis=1))

1	[91 52 26]