使用matplotlib在熊猫中以对数比例绘制x和y轴

Question

My trace file can be downloaded from here .

When I plot only y axis in log scale. everything is fine

import pandas as pd
import numpy
import matplotlib.pyplot as plt

iplevel = pd.read_csv('iplevel.csv')
fig = plt.figure()
#plt.xscale('log')
plt.yscale('log')
plt.title(' Size Vs Duration (at IP level) for ')

plt.xlabel('Duration (in seconds)')
plt.ylabel('Size (in bytes)')
plt.scatter(iplevel['Time'], iplevel['Length'])
fig.tight_layout()
fig.savefig('iplevel_timevdur.png', dpi=fig.dpi)

When I plot both x and y axis in log scale, something strange happens

import pandas as pd
import numpy
import matplotlib.pyplot as plt

iplevel = pd.read_csv('iplevel.csv')
fig = plt.figure()
plt.xscale('log')
plt.yscale('log')
plt.title(' Size Vs Duration (at IP level) for ')

plt.xlabel('Duration (in seconds)')
plt.ylabel('Size (in bytes)')
plt.scatter(iplevel['Time'], iplevel['Length'])
fig.tight_layout()
fig.savefig('iplevel_timevdur.png', dpi=fig.dpi)

I am not sure where I am going wrong. Any ideas/suggestions welcome

Answer 1

It looks like you have some zeros in your X values. log(0) isn't defined, log(veryclosetozero) is 10^{-verymuch} .

Edit:
In addition, float representation of numbers isn't always completely exact, so 0.0 might end up being stored as 0.00000000000000000001 or similar. The log function would not throw an error in that case, but simply calculate the logarithm of something very very small.

Answer 2

I faced a similar problem when plotting numbers containing a lot of zeros. If your number is represented like 10E-38 format in the csv file, try multiplying all the rows by 1 and then read the data using pandas.

This solved the problem in my case.