📅 最后修改于: 2020-10-27 04:12:49 🧑 作者: Mango
Numpy包含大量数学函数，可用于执行各种数学运算。数学函数包括三角函数，算术函数和用于处理复数的函数。让我们讨论一下数学函数。
Numpy包含用于计算弧度中不同角度的正弦，余弦和正切的三角函数。
sin，cos和tan函数返回指定角度的三角比。考虑以下示例。
import numpy as np
arr = np.array([0, 30, 60, 90, 120, 150, 180])
print("\nThe sin value of the angles",end = " ")
print(np.sin(arr * np.pi/180))
print("\nThe cosine value of the angles",end = " ")
print(np.cos(arr * np.pi/180))
print("\nThe tangent value of the angles",end = " ")
print(np.tan(arr * np.pi/180))
输出：
The sin value of the angles
[0.00000000e+00 5.00000000e-01 8.66025404e-01 1.00000000e+00
8.66025404e-01 5.00000000e-01 1.22464680e-16]
The cosine value of the angles
[ 1.00000000e+00 8.66025404e-01 5.00000000e-01 6.12323400e-17
-5.00000000e-01 -8.66025404e-01 -1.00000000e+00]
The tangent value of the angles [ 0.00000000e+00 5.77350269e-01 1.73205081e+00 1.63312394e+16
-1.73205081e+00 -5.77350269e-01 -1.22464680e-16]
另一方面，arcsin()，arccos()和arctan()函数返回指定角度的三角逆。
numpy.degrees()函数可用于验证这些三角函数的结果。考虑以下示例。
import numpy as np
arr = np.array([0, 30, 60, 90])
print("printing the sin values of different angles")
sinval = np.sin(arr*np.pi/180)
print(sinval)
print("printing the inverse of the sin")
cosec = np.arcsin(sinval)
print(cosec)
print("printing the values in degrees")
print(np.degrees(cosec))
print("\nprinting the cos values of different angles")
cosval = np.cos(arr*np.pi/180)
print(cosval)
print("printing the inverse of the cos")
sec = np.arccos(cosval)
print(sec)
print("\nprinting the values in degrees")
print(np.degrees(sec))
print("\nprinting the tan values of different angles")
tanval = np.tan(arr*np.pi/180)
print(tanval)
print("printing the inverse of the tan")
cot = np.arctan(tanval)
print(cot)
print("\nprinting the values in degrees")
print(np.degrees(cot))
输出：
printing the sin values of different angles
[0. 0.5 0.8660254 1. ]
printing the inverse of the sin
[0. 0.52359878 1.04719755 1.57079633]
printing the values in degrees
[ 0. 30. 60. 90.]
printing the cos values of different angles
[1.00000000e+00 8.66025404e-01 5.00000000e-01 6.12323400e-17]
printing the inverse of the cos
[0. 0.52359878 1.04719755 1.57079633]
printing the values in degrees
[ 0. 30. 60. 90.]
printing the tan values of different angles
[0.00000000e+00 5.77350269e-01 1.73205081e+00 1.63312394e+16]
printing the inverse of the tan
[0. 0.52359878 1.04719755 1.57079633]
printing the values in degrees
[ 0. 30. 60. 90.]
numpy提供了各种功能，可用于截断十进制浮点数的值，将其舍入为十进制数的特定精度。让我们讨论舍入函数。
此函数返回一个十进制值，四舍五入到十进制的所需位置。该函数的语法如下。
numpy.around(num, decimals)
它接受以下参数。
| SN | Parameter | Description |
|---|---|---|
| 1 | num | It is the input number. |
| 2 | decimals | It is the number of decimals which to which the number is to be rounded. The default value is 0. If this value is negative, then the decimal will be moved to the left. |
考虑以下示例。
import numpy as np
arr = np.array([12.202, 90.23120, 123.020, 23.202])
print("printing the original array values:",end = " ")
print(arr)
print("Array values rounded off to 2 decimal position",np.around(arr, 2))
print("Array values rounded off to -1 decimal position",np.around(arr, -1))
输出：
printing the original array values: [ 12.202 90.2312 123.02 23.202 ]
Array values rounded off to 2 decimal position [ 12.2 90.23 123.02 23.2 ]
Array values rounded off to -2 decimal position [ 10. 90. 120. 20.]
此函数用于返回输入数据的下限值，该下限值是不大于输入值的最大整数。考虑以下示例。
import numpy as np
arr = np.array([12.202, 90.23120, 123.020, 23.202])
print(np.floor(arr))
输出：
[ 12. 90. 123. 23.]
此函数用于返回数组值的上限值，该值是大于数组元素的最小整数值。考虑以下示例。
import numpy as np
arr = np.array([12.202, 90.23120, 123.020, 23.202])
print(np.ceil(arr))
输出：
[ 13. 91. 124. 24.]