NumPy 数学函数
很容易理解,NumPy 包含大量的各种数学运算。 NumPy 提供标准三角函数、算术运算、处理复数等函数。
三角函数
NumPy 具有标准三角函数,它返回给定角度的三角比(以弧度为单位)。
import numpy as np a = np.array([0,30,45,60,90]) print 'Sine of different angles:' # Convert to radians by multiplying with pi/180 print np.sin(a*np.pi/180) print '\n' print 'Cosine values for angles in array:' print np.cos(a*np.pi/180) print '\n' print 'Tangent values for given angles:' print np.tan(a*np.pi/180)
输出:
Sine of different angles: [ 0. 0.5 0.70710678 0.8660254 1. ] Cosine values for angles in array: [ 1.00000000e+00 8.66025404e-01 7.07106781e-01 5.00000000e-01 6.12323400e-17] Tangent values for given angles: [ 0.00000000e+00 5.77350269e-01 1.00000000e+00 1.73205081e+00 1.63312394e+16]
arcsin、arcos和arctan函数返回给定角度的sin、cos和tan的三角逆运算。这些函数的结果可以通过numpy.degree()函数将弧度转换为度来验证。
import numpy as np a = np.array([0,30,45,60,90]) print 'Array containing sine values:' sin = np.sin(a*np.pi/180) print sin print '\n' print 'Compute sine inverse of angles. Returned values are in radians.' inv = np.arcsin(sin) print inv print '\n' print 'Check result by converting to degrees:' print np.degrees(inv) print '\n' print 'arccos and arctan functions behave similarly:' cos = np.cos(a*np.pi/180) print cos print '\n' print 'Inverse of cos:' inv = np.arccos(cos) print inv print '\n' print 'In degrees:' print np.degrees(inv) print '\n' print 'Tan function:' tan = np.tan(a*np.pi/180) print tan print '\n' print 'Inverse of tan:' inv = np.arctan(tan) print inv print '\n' print 'In degrees:' print np.degrees(inv)
其输出如下:
Array containing sine values: [ 0. 0.5 0.70710678 0.8660254 1. ] Compute sine inverse of angles. Returned values are in radians. [ 0. 0.52359878 0.78539816 1.04719755 1.57079633] Check result by converting to degrees: [ 0. 30. 45. 60. 90.] arccos and arctan functions behave similarly: [ 1.00000000e+00 8.66025404e-01 7.07106781e-01 5.00000000e-01 6.12323400e-17] Inverse of cos: [ 0. 0.52359878 0.78539816 1.04719755 1.57079633] In degrees: [ 0. 30. 45. 60. 90.] Tan function: [ 0.00000000e+00 5.77350269e-01 1.00000000e+00 1.73205081e+00 1.63312394e+16] Inverse of tan: [ 0. 0.52359878 0.78539816 1.04719755 1.57079633] In degrees: [ 0. 30. 45. 60. 90.]
舍入函数
numpy.around()
这是一个返回四舍五入到所需精度的值的函数。该函数采用以下参数。
numpy.around(a,decimals)
序号. | 参数及说明 |
---|---|
1 | a 输入数据 |
2 | decimals 要四舍五入的小数位数。默认为 0。如果为负,则整数四舍五入到小数点左侧的位置 |
import numpy as np a = np.array([1.0,5.55, 123, 0.567, 25.532]) print 'Original array:' print a print '\n' print 'After rounding:' print np.around(a) print np.around(a, decimals = 1) print np.around(a, decimals = -1)
它产生以下输出:
Original array: [ 1. 5.55 123. 0.567 25.532] After rounding: [ 1. 6. 123. 1. 26. ] [ 1. 5.6 123. 0.6 25.5] [ 0. 10. 120. 0. 30. ]
numpy.floor()
此函数返回不大于输入参数的最大整数。的地板scalar x是最大的integer i,这样我 <= x.请注意,在 Python 中,地板总是从 0 舍入。
import numpy as np a = np.array([-1.7, 1.5, -0.2, 0.6, 10]) print 'The given array:' print a print '\n' print 'The modified array:' print np.floor(a)
它产生以下输出:
The given array: [ -1.7 1.5 -0.2 0.6 10. ] The modified array: [ -2. 1. -1. 0. 10.]
numpy.ceil()
ceil() 函数返回输入值的上限,即scalar x是最小的integer i,这样i >= x。
import numpy as np a = np.array([-1.7, 1.5, -0.2, 0.6, 10]) print 'The given array:' print a print '\n' print 'The modified array:' print np.ceil(a)
它将产生以下输出:
The given array: [ -1.7 1.5 -0.2 0.6 10. ] The modified array: [ -1. 2. -0. 1. 10.]