Python 中的 numpy.log2()
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numpy.log2(arr，out = None，*其中= True，casting = 'same_kind '，order = 'K '，dtype = None，ufunc 'log1p') : 这个数学函数帮助用户计算x 的 2 底对数，其中 x 属于所有输入数组元素。
参数:
array : [array_like]Input array or object.
out : [ndarray, optional]Output array with same dimensions as Input array,
placed with result.
**kwargs : Allows you to pass keyword variable length of argument to a function.
It is used when we want to handle named argument in a function.
where : [array_like, optional]True value means to calculate the universal
functions(ufunc) at that position, False value means to leave the
value in the output alone.
返回:
An array with Base-2 logarithmic value of x;
where x belongs to all elements of input array.
代码 1:工作
# Python program explaining
# log2() function
import numpy as np
in_array = [1, 3, 5, 2**8]
print ("Input array : ", in_array)
out_array = np.log2(in_array)
print ("Output array : ", out_array)
print("\nnp.log2(4**4) : ", np.log2(4**4))
print("np.log2(2**8) : ", np.log2(2**8))
输出:
Input array : [1, 3, 5, 256]
Output array : [ 0\. 1.5849625 2.32192809 8\. ]
np.log2(4**4) : 8.0
np.log2(2**8) : 8.0
代码 2:图形表示
# Python program showing
# Graphical representation of
# log2() function
import numpy as np
import matplotlib.pyplot as plt
in_array = [1, 1.2, 1.4, 1.6, 1.8, 2]
out_array = np.log2(in_array)
print ("out_array : ", out_array)
plt.plot(in_array, in_array, color = 'blue', marker = "*")
# red for numpy.log2()
plt.plot(out_array, in_array, color = 'red', marker = "o")
plt.title("numpy.log2()")
plt.xlabel("out_array")
plt.ylabel("in_array")
plt.show()
输出:
out_array : [ 0\. 0.26303441 0.48542683 0.67807191 0.84799691 1\. ]
参考文献:
https://docs . scipy . org/doc/numpy-1 . 13 . 0/reference/generated/numpy . exp . html
。
