Dealing with plotting negative, zero and positive values in log scale

Sometimes you have to show positive, zero and negative number in log scale. However you cannot take log of negative numbers and zero. But one could approximate it with a log transform modulus as stated here.

In Python with numpy:

from numpy import sign, abs, log10
import matplotlib.pyplot as plt

# Data varies in several magnitudes and has both positive, zero and negative numbers
x = [-10000,-1000,-100,-10,0,10,100,1000,10000]
# log modulus transform
x_log_modulus_transform= sign(x)*(log10(abs(x)+1))

f, ax = plt.subplots(2, sharex=True)


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>