版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/bless2015/article/details/81670973
加/减
import numpy as np
a=np.array([10,20,30,40])
b=np.arange(4)
print(a,b) //[10 20 30 40] [0 1 2 3]
c = a+b
print(c) //[10 21 32 43]
乘方
c = b**2
print(c) //[0 1 4 9]
三角函数
c = 10*np.sin(a)
print(c) //[-5.44021111 9.12945251 -9.88031624 7.4511316 ]
//还有
//np.cos() np.tan()
按条件统计
print(b<3) //[ True True True False]
print(b==3) //[False False False True]
矩阵运算
a = np.array([[1,1],
[0,1]])
b = np.arange(4).reshape((2,2))
print(a) //[[1 1]
//[0 1]]
print(b) //[[0 1]
//[2 3]]
//点乘
c = a*b
//矩阵乘
c_dot = np.dot(a,b)
//或
c_dot2 = a.dot(b)
print(c) //[[0 1]
//[0 3]]
print(c_dot) //[[2 4]
//[2 3]]
求array和、最小值、最大值
import numpy as np
a = np.random.random((2,4))
np.sum(a)
np.max(a)
np.mim(a)
//求某一行(维度)
np.sum(a,axis=1) //每行上求和
np.max(a,axis=0) //每列上求最大值
np.min(a,axis=1) //每行上求最小值
其他运算
A = np.arange(2,14).reshape((3,4))
print(A) //[[ 2 3 4 5]
// [ 6 7 8 9]
// [10 11 12 13]]
min_index = np.argmin(A) //最小值下标
max_index = np.argmax(A) //最大值小标
mean = np.mean(A) //平均值
//或
//A.mean()
median = np.median(A) //中位数
cumsum = np.cumsum(A) //累加
diff = np.diff(A) //临差
nonzero = np.nonzero(A) //非零元素所在的行和列
sort = np.sort(A) //排序
tran = np.transpose(A) //矩阵转置
//或
A.T
例如
A.T.dot(A)
clip = np.clip(A,5,9) //所有小于5的都等于5,所有大于9的都等于9
np.mean(A,axis=0) //按列进行计算求平均值
print(min_index) //0
print(max_index) //11
print(mean) //7.5
print(median) //7.5
print(cumsum) //[ 2 5 9 14 20 27 35 44 54 65 77 90]
print(diff) //[[1 1 1]
// [1 1 1]
// [1 1 1]]
print(nonzero) //(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))
//另一种老版本平均值算法
np.average(A)