python-对seaborn使用科学计数法

Question

I'm trying to create a kde plot using seaborn in python but when setting the colorbar values to show in scientific notation I see no difference.

See - making colorbar with scientific notation in seaborn for a heavily related topic.

See - https://seaborn.pydata.org/generated/seaborn.kdeplot.html for the documentation of seaborn's kde class.

Is there some reason why this doesn't work for the kde class or am I making a silly mistake in my formatting?

import numpy as np
import seaborn as sns
import matplotlib.ticker as tkr

a = np.random.normal(0,1,size=100)
b = np.random.normal(0,1,size=100)

fig, ax = plt.figure(), plt.subplot(111)
formatter = tkr.ScalarFormatter(useMathText=True)
formatter.set_scientific(True)
sns.kdeplot(a,b, n_levels=10, shade=True, cmap='Blues',
            cbar=True, cbar_kws={'format':formatter})

The result:

Here I would be expecting the colourbar to show an indexed notation as in the first link in the description of this problem.

Many thanks in advance!

Answer 1

.set_scientific(True) applies to the offset label. Here you don't have any offset, so it seems like it's ignored. There is unfortunately no canonical way to format the ticklabels themselves in scientific notation.

One method is shown in Can I show decimal places and scientific notation on the axis of a matplotlib plot using Python 2.7?

Applying it here:

import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker

a = np.random.normal(0,1,size=100)
b = np.random.normal(0,1,size=100)

fig, ax = plt.figure(), plt.subplot(111)

f = mticker.ScalarFormatter(useOffset=False, useMathText=True)
g = lambda x,pos : "${}$".format(f._formatSciNotation('%1.10e' % x))

sns.kdeplot(a,b, n_levels=10, shade=True, cmap='Blues',
            cbar=True, cbar_kws={'format': mticker.FuncFormatter(g)})

plt.show()