CODEWITHSUNDEEP
pythonmatplotlibhistogramscatter-plot
astromax
astromax

Reputation: 6331

Matplotlib Scatter and Histogram

I'm trying to plot some data using Matplotlib's 2d scatterplot function while at the same time, producing projected histograms on the x and y axes. The example I've found comes right from the matplotlib image gallery (pylab_examples example code: scatter_hist.py).

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.ticker import NullFormatter

# the random data
x = np.random.randn(1000)
y = np.random.randn(1000)

nullfmt   = NullFormatter()         # no labels

# definitions for the axes
left, width = 0.1, 0.65
bottom, height = 0.1, 0.65
bottom_h = left_h = left+width+0.02

rect_scatter = [left, bottom, width, height]
rect_histx = [left, bottom_h, width, 0.2]
rect_histy = [left_h, bottom, 0.2, height]

# start with a rectangular Figure
plt.figure(1, figsize=(8,8))

axScatter = plt.axes(rect_scatter)
axHistx = plt.axes(rect_histx)
axHisty = plt.axes(rect_histy)

# no labels
axHistx.xaxis.set_major_formatter(nullfmt)
axHisty.yaxis.set_major_formatter(nullfmt)

# the scatter plot:
axScatter.scatter(x, y)

# now determine nice limits by hand:
binwidth = 0.25
xymax = np.max( [np.max(np.fabs(x)), np.max(np.fabs(y))] )
lim = ( int(xymax/binwidth) + 1) * binwidth

axScatter.set_xlim( (-lim, lim) )
axScatter.set_ylim( (-lim, lim) )

bins = np.arange(-lim, lim + binwidth, binwidth)

axHistx.hist(x, bins=bins)
axHisty.hist(y, bins=bins, orientation='horizontal')

axHistx.set_xlim( axScatter.get_xlim() )
axHisty.set_ylim( axScatter.get_ylim() )

plt.show()

The only problem is that the example doesn't work. I get the following error: 

~$ python ~/Desktop/scatter_and_hist.py 
Traceback (most recent call last):
  File "/Users/username/Desktop/scatter_and_hist.py", line 45, in <module>
    axHisty.hist(y, bins=bins, orientation='horizontal')
  File "//anaconda/lib/python2.7/site-packages/matplotlib/axes.py", line 8180, in hist
    color=c, bottom=bottom)
TypeError: barh() got multiple values for keyword argument 'bottom'

I've gone through the code and isolated the problem. It's line #45 (axHisty.hist(y, bins=bins, orientation='horizontal')) which is causing the problem. It's so frustrating to see the plot you want in their image library, but have the example not work. A second set of eyes would be greatly appreciated!

Upvotes: 4

Views: 4634

Answers (1)

tacaswell
tacaswell

Reputation: 87376

You have hit a bug in v1.2.1 (https://github.com/matplotlib/matplotlib/pull/1985). You can upgrade your matplotlib, monkey patch your version with the bug-fix, or use np.histogram and call barh with the correct order of arguments your self.

As a side note, the only code necessary for this question is:

x = np.random.rand(100)
plt.hist(x, orientation='horizontal')
plt.show()

everything else you posted is noise.

Upvotes: 5

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