在地图上绘制饼图时“爆炸”楔形图（Python，matplotlib）

Question

所以我成功地在地图上绘制了饼图作为标记轴向散射，但我遇到了一些问题，一些楔子“爆炸”出了饼图。我似乎在我的代码中找不到原因，也无法在网上找到解释。这段代码基于示例here，一位同事也使用了这个示例并生成了普通的、统一的饼图。我们之间找不到问题，也没有出错。在

代码：

import numpy as np
import math
import matplotlib
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap, cm

australia_data = np.zeros((24,12))
colors = ['red','yellow','blue','mediumorchid']

#pie chart locations
xlon=[146.7,166,101.6,137.4,145.1,113.6,169.7,113.3,176.0,139.6,148.9,124.2,132.4,142.0,129.6,148.0,116.5,142.8,141.7,128.0,113.6,120.7,128.3,148.6]          
ylat=[-42.2,-19.2,-0.5,-3.5,-34.4,-8.7,-45.1,-1.0,-38.6,-26.7,-29.1,-20.0,-14.4,-18.9,-31.3,-6.6,-23.8,-3.4,-7.5,-25.6,3.8,-3.1,-1.9,-23.2]

#function to draw pie charts on map
def draw_pie(ax,X=0, Y=0, size = 1500): 
    xy = []
    start = 0.17 
    ratios=[1/12.]*12
    for ratio in ratios:
        x = [0] + np.cos(np.linspace(2*math.pi*start,2*math.pi*(start+ratio))).tolist() #30
        y = [0] + np.sin(np.linspace(2*math.pi*start,2*math.pi*(start+ratio))).tolist() #30
        xy1=(zip(x,y))
        xy.append(xy1)
        start -= ratio

    piecolors = []
    for lt in range(12):
        c = australia_data[b,lt]-1
        c=int(c)
        piecolors.append(colors[c])

    for i, xyi in enumerate(xy):
       ax.scatter([X],[Y] , marker=(xyi,0), s=size, facecolor=piecolors[i],linewidth=0.5,alpha=.7)

australia_data[:,11] = 1
australia_data[:,4] = 3
australia_data[:,1] = 2

fig = plt.figure()
ax = fig.add_axes([.05,.01,.79,.95]) 

x1 = 90 #left
x2 = 180 #right
y1 = -50 #bottom
y2 = 10 #top          

#Create the map 
m = Basemap(resolution='l',projection='merc', llcrnrlat=y1,urcrnrlat=y2,llcrnrlon=x1,urcrnrlon=x2,lat_ts=0) #,lat_ts=(x1+x2)/2
m.drawcoastlines()            

#plots pie charts:
for b in range(24):
    X,Y=m(xlon[b],ylat[b]) 
    draw_pie(ax,X, Y,size=400)


plt.savefig('australia_pies.png',dpi=400)

有什么想法知道为什么会发生这种情况（以及如何解决它！）不胜感激！ 编辑：这似乎是一个饼图中楔子数量的问题-减少到6将导致均匀的饼图，但7+会导致一些楔子“爆炸”。在

Answer 1

看着scatter piecharts example，您忘记了根据从0到楔形弧的最大距离来调整饼图楔体的大小。这是必要的，因为标记在绘制路径之前将其规范化，因此不同的楔体需要不同的大小，以便在最终绘图中以相同的大小显示。在

import numpy as np
import matplotlib.pyplot as plt

#function to draw pie charts on map
def draw_pie(ax,X=0, Y=0, size = 1500): 
    xy = []; s=[]
    start = 0.0 
    ratios=[1/12.]*12
    for ratio in ratios:
        x = [0] + np.cos(np.linspace(2*np.pi*start,2*np.pi*(start+ratio))).tolist() #30
        y = [0] + np.sin(np.linspace(2*np.pi*start,2*np.pi*(start+ratio))).tolist() #30

        xy1 = np.column_stack([x, y])
        s1 = np.abs(xy1).max()

        xy.append(xy1)
        s.append(s1)
        start -= ratio

    for xyi, si in zip(xy,s):
       ax.scatter([X],[Y] , marker=(xyi,0), s=size*si**2, edgecolor="k")

fig, ax = plt.subplots() 

X,Y=166,50 
draw_pie(ax,X, Y,size=3000)

plt.show()