有人可以解释一下np.log的作用吗? [英] Can some one explain me what does np.log do?

问题描述

我知道这是一个简单的问题，但是我无法获得np.log的确切功能?我看到了文档，但是我无法了解np.log背后的逻辑. np.log([9000000])我得到的输出为16.01273514.我不明白为什么要得到这个号码，我知道什么是

I understand that this is a simple question, but I couldnt get what exactly does np.log do? I saw the documentation from which I am not able to understand the logic behind np.log. np.log([9000000]) I am getting the output as 16.01273514. I couldnt understand why I am getting this number, I fo know what a logarithm means.

推荐答案

np.log(x)是自然对数，即必须将e的幂提高到等于x:

np.log(x) is the natural logarithm, i.e. the power to which e would have to be raised to equal x:

>>> np.log([1, np.e, np.e**2, 0])
array([  0.,   1.,   2., -Inf])

以10为底的对数:

>>> np.log10([1e-15, -3.])
array([-15.,  NaN])

以2为底的对数:

>>> x = np.array([0, 1, 2, 2**4])
>>> np.log2(x)
array([-Inf,   0.,   1.,   4.])

在您的示例中:

>>> np.log([9000000])        # ln(9000000)
array([ 16.01273514])

>>> np.exp([16.01273514])    # e^16
array([ 9000000.04229556])

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