Matplotlib更改栏颜色

Question

Matplotlib changes the color of the bar when there are more values plotted : With 5 columns I get the expected red bars :

ax = vc[vc.index[:5]].plot(color='red', kind='bar', title=col+('(count)'))

    ax.set_axis_bgcolor('white')

But going for more values, the colors begin to fade and there is some grey bars appearing :(

ax = vc.plot(color='red', kind='bar', title=col+('(count)'))
ax.set_axis_bgcolor('white')

How can I keep My red bars all along ?

Answer 1

They probably become gray because of the edge colors of the bars:

import matplotlib.pylab as pl
import numpy as np
import pandas as p

pl.figure()

x = np.arange(5)
y = np.random.random(x.size)
vc1 = p.DataFrame(data=y, index=x)

x = np.arange(100)
y = np.random.random(x.size)
vc2 = p.DataFrame(data=y, index=x)

ax = pl.subplot(131)
vc1.plot(ax=ax, kind='bar', color='red')

ax = pl.subplot(132)
vc2.plot(ax=ax, kind='bar', color='red')

ax = pl.subplot(133)
vc2.plot(ax=ax, kind='bar', color='red', edgecolor='none')