如何从ax.pcolormesh密度图中删除矩形的白色边框？

如何解决如何从ax.pcolormesh密度图中删除矩形的白色边框？

from mplsoccer.pitch import Pitch
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import kde

np.random.seed(19680801)
plt.style.use('dark_background')
fields = ['id','minute','result','X1','Y','xG','h_a','situation','season','shottype','X']
df=pd.read_csv('shots.csv',skipinitialspace=True,usecols=fields)

df1 = pd.DataFrame({'A':df.Y,'B':df.X} )
a=(df1.to_numpy())
x,y = a.T
k = kde.gaussian_kde(a.T)

nbins=50

xi,yi = np.mgrid[x.min():x.max():nbins*1j,y.min():y.max():nbins*1j]
zi = k(np.vstack([xi.flatten(),yi.flatten()]))

pitch = Pitch(orientation='vertical',pitch_type='metricasports',view='half',linewidth=2,line_zorder=1,line_color= '#94A7AE',pitch_length=105,pitch_width=68,pad_bottom=0)

fig,ax = pitch.draw()
ax.pcolormesh(xi,yi,zi.reshape(xi.shape),shading='gouraud',cmap='Reds',facecolor='black'
              )

ax.set_xlim(ax.get_xlim()[::-1])       
ax.yaxis.tick_right()  
plt.axis('off')
plt.show()

Output Plot here

我想要唯一的红色密度图，而不是白色矩形背景框。如何使框架与背景相同？

解决方法

这是一种使用"under" color为'none'的色图的方法。通过将vmin设置为截止值，值较低的像元将获得“下”色（“无”代表完全透明）。为了了解这些值，可以临时添加一个颜色栏。这些值在很大程度上取决于x和y值的扩展（kde的积分为1，因此在较小的域中，这些值必须足够高）。

from mplsoccer.pitch import Pitch
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import kde
from copy import copy

np.random.seed(19680801)
plt.style.use('dark_background')
# first create some random toy data roughly mimicking the given plot
x = np.random.randn(100,20).cumsum(axis=0).flatten()
y = np.random.randn(100,20).cumsum(axis=0).flatten()
x = x * 0.04 + 0.5
y = y * 0.01 + 0.9
k = kde.gaussian_kde([x,y])

nbins = 50
xi,yi = np.mgrid[x.min():x.max():nbins * 1j,y.min():y.max():nbins * 1j]
zi = k(np.vstack([xi.flatten(),yi.flatten()]))

pitch = Pitch(orientation='vertical',pitch_type='metricasports',view='half',linewidth=2,line_zorder=1,line_color='#94A7AE',pitch_length=105,pitch_width=68,pad_bottom=0)

fig,ax = pitch.draw()
cmap = copy(plt.get_cmap('Reds'))
cmap.set_under('none')
pmesh = ax.pcolormesh(xi,yi,zi.reshape(xi.shape),shading='gouraud',cmap=cmap,vmin=5,facecolor='black')
# fig.colorbar(pmesh,ax=ax) # to temporarily get an idea of the values
ax.invert_xaxis()
ax.yaxis.tick_right()
plt.axis('off')
plt.show()