Numpy 基础运算2

# -*- encoding:utf-8 -*-
# Copyright (c) 2015 Shiye Inc.
# All rights reserved.
#
# Author: ldq <liangduanqi@shiyejinrong.com>
# Date: 2019/2/11 14:57

import numpy as np


a = np.arange(2, 14).reshape(3, 4)
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reshape矩阵变维
[[ 2  3  4  5]
 [ 6  7  8  9]
 [10 11 12 13]]
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a_arg_max = np.argmax(a)
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返回最大索引
11
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mean_a = np.mean(a)
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mean平均值
7.5
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avg_a = np.average(a)
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average加权平均值
7.5
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mean_x = np.mean(np.array([1,2,3,4,5]))
average_x = np.average(np.array([1,2,3,4,5]), weights=np.array([1,1,1,1,1]))
median_a = np.median(a)
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median中位数
7.5
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cumsum_a = np.cumsum(a)
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cumsum元素累加
[ 2  5  9 14 20 27 35 44 54 65 77 90]
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diff_a = np.diff(a, axis=0)
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数值差分
[[4 4 4 4]
 [4 4 4 4]]
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nonzero_a = np.nonzero(a)
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nonzero这个函数将所有非零元素的行与列坐标分割开，重构成两个分别关于行和列的矩阵
(array([0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2], dtype=int64), array([0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3], dtype=int64))
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sort_a = np.sort(a,axis=-1,kind=‘mergesort‘)

transpose_a = np.transpose(a)
transpose_a_2 = a.T
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矩阵的转置
transpose
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clip_a = np.clip(a,5,9)
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clip指定的元素转换为最小值或者最大值
[[5 5 5 5]
 [6 7 8 9]
 [9 9 9 9]]
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