pylab: " NameError: global name 'log' is not defined " how to import log function in pylab?

[typetoken]

I want to draw a plot with the y axis in a 'logarithmic scale'. However, it pops up " NameError: global name 'log' is not defined ". Does anyone know how to import log in this case? Thanks indeed.

>>> def zif(text):

fdist = nltk.FreqDist(text)

import pylab

word = fdist.keys()

x = []

y = []

index = []

for i in range(0,len(set(text)),1):

x.extend(word[i:i+1])

y.extend([fdist[word[i]]])

index.extend([i+1])

pylab.plot(index, log(y),'-bo')

pylab.title('zipf law')

pylab.xlabel('word rank')

pylab.ylabel('word frequency')

pylab.show()

>>> zif(text)

Traceback (most recent call last):

  File "<pyshell#141>", line 1, in <module>

    zif(text)

  File "<pyshell#140>", line 12, in zif

    pylab.plot(index, log(y),'-bo')

NameError: global name 'log' is not defined

[Correa Denzil]

To be quite honest, I doubt this group is an appropriate place to ask questions which are not related to NLTK. But, here's my off hand try to your solution

import numpy as np

y_np = np.array(y)

np.log(y_np)

--Regards,
Denzil

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[John H. Li]

Thanks. I've found other solutions from the later chapter of the nltk book (cf P218):

replace pylab.plot with

pylab.semilogy() for log in y axis, or

pylab.semilogx() for log in x axis

But what if we want log in both x and y axis?