是python画图系列第三篇--饼图

画饼图用到的方法为：

matplotlib.pyplot.pie()

参数为：

pie(x, explode=None, labels=None,
 colors=('b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'),
 autopct=None, pctdistance=0.6, shadow=False,
 labeldistance=1.1, startangle=None, radius=None,
 counterclock=True, wedgeprops=None, textprops=None,
 center=(0, 0), frame=False )

参数说明：

x (每一块)的比例，如果sum(x) > 1会使用sum(x)归一化

labels (每一块)饼图外侧显示的说明文字

explode (每一块)离开中心距离

startangle 起始绘制角度,默认图是从x轴正方向逆时针画起,如设定=90则从y轴正方向画起

shadow 是否阴影

labeldistance label绘制位置,相对于半径的比例, 如<1则绘制在饼图内侧

autopct 控制饼图内百分比设置,可以使用format字符串或者format function

'%1.1f'指小数点前后位数(没有用空格补齐)

pctdistance 类似于labeldistance,指定autopct的位置刻度

radius 控制饼图半径

返回值:

如果没有设置autopct,返回(patches, texts)

如果设置autopct,返回(patches, texts, autotexts)

patches -- list --matplotlib.patches.Wedge对象

texts autotexts -- matplotlib.text.Text对象

下面是一个简单的示例：

# -*- coding: utf-8 -*-
import numpy as np 
import matplotlib.mlab as mlab 
import matplotlib.pyplot as plt 
labels=['China','Swiss','USA','UK','Laos','Spain']
X=[222,42,455,664,454,334] 
 
fig=plt.figure()
plt.pie(X,labels=labels,autopct='%1.2f%%') #画饼图（数据，数据对应的标签，百分数保留两位小数点）
plt.title("Pie chart")
 
 
plt.show() 
plt.savefig("PieChart.jpg")

下面是结果：

下面是另一个示例：

# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt
import matplotlib as mpl
 
def draw_pie(labels,quants):
 # make a square figure
 plt.figure(1, figsize=(6,6))
 # For China, make the piece explode a bit
 expl=[0,0.1,0,0,0,0,0,0,0,0] #第二块即China离开圆心0.1
 # Colors used. Recycle if not enough.
 colors=["blue","red","coral","green","yellow","orange"] #设置颜色（循环显示）
 # Pie Plot
 # autopct: format of "percent" string;百分数格式
 plt.pie(quants, explode=expl, colors=colors, labels=labels, autopct='%1.1f%%',pctdistance=0.8, shadow=True)
 plt.title('Top 10 GDP Countries', bbox={'facecolor':'0.8', 'pad':5})
 plt.show()
 plt.savefig("pie.jpg")
 plt.close()
 
# quants: GDP
 
# labels: country name
 
labels=['USA', 'China', 'India', 'Japan', 'Germany', 'Russia', 'Brazil', 'UK', 'France', 'Italy']
 
quants=[15094025.0, 11299967.0, 4457784.0, 4440376.0, 3099080.0, 2383402.0, 2293954.0, 2260803.0, 2217900.0, 1846950.0]
 
draw_pie(labels,quants)

官方文档：

链接：http://matplotlib.org/api/pyplot_api.html

matplotlib.pyplot.pie(x, explode=None, labels=None, colors=None, autopct=None, pctdistance=0.6, shadow=False, labeldistance=1.1, startangle=None,radius=None, counterclock=True, wedgeprops=None, textprops=None, center=(0, 0), frame=False, hold=None, data=None)Plot a pie chart.

Call signature:

pie(x, explode=None, labels=None,
 colors=('b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'),
 autopct=None, pctdistance=0.6, shadow=False,
 labeldistance=1.1, startangle=None, radius=None,
 counterclock=True, wedgeprops=None, textprops=None,
 center=(0, 0), frame=False )

Make a pie chart of array x. The fractional area of each wedge is given by x/sum(x). If sum(x) <=1, then the values of x give the fractional area directly and the array will not be normalized. The wedges are plotted counterclockwise, by default starting from the x-axis.

Keyword arguments:

explode: [ None | len(x) sequence ]

If not None, is a len(x) array which specifies the fraction of the radius with which to offset each wedge.

colors: [ None | color sequence ]

A sequence of matplotlib color args through which the pie chart will cycle.

labels: [ None | len(x) sequence of strings ]

A sequence of strings providing the labels for each wedge

autopct: [ None | format string | format function ]

If not None, is a string or function used to label the wedges with their numeric value. The label will be placed inside the wedge. If it is a format string, the label will be fmt%pct. If it is a function, it will be called.

pctdistance: scalar

The ratio between the center of each pie slice and the start of the text generated by autopct. Ignored if autopct is None; default is 0.6.

labeldistance: scalar

The radial distance at which the pie labels are drawn

shadow: [ False | True ]

Draw a shadow beneath the pie.

startangle: [ None | Offset angle ]

If not None, rotates the start of the pie chart by angle degrees counterclockwise from the x-axis.

radius: [ None | scalar ] The radius of the pie, if radius is None it will be set to 1.

counterclock: [ False | True ]

Specify fractions direction, clockwise or counterclockwise.

wedgeprops: [ None | dict of key value pairs ]

Dict of arguments passed to the wedge objects making the pie. For example, you can pass in wedgeprops={ ‘linewidth’ : 3 } to set the width of the wedge border lines equal to 3. For more details, look at the doc/arguments of the wedge object. By default clip_on=False.

textprops: [ None | dict of key value pairs ]

Dict of arguments to pass to the text objects.

center: [ (0,0) | sequence of 2 scalars ] Center position of the chart.

frame: [ False | True ]

Plot axes frame with the chart.

The pie chart will probably look best if the figure and axes are square, or the Axes aspect is equal. e.g.:

figure(figsize=(8,8))
ax=axes([0.1, 0.1, 0.8, 0.8])

or:

axes(aspect=1)

Return value:

If autopct is None, return the tuple (patches, texts):

• patches is a sequence of matplotlib.patches.Wedge instances
• texts is a list of the label matplotlib.text.Text instances.

If autopct is not None, return the tuple (patches, texts, autotexts), where patches and texts are as above, and autotexts is a list of Textinstances for the numeric labels.

Notes

In addition to the above described arguments, this function can take a data keyword argument. If such a data argument is given, the following arguments are replaced by data[<arg>]:

• All arguments with the following names: ‘colors’, ‘x’, ‘explode’, ‘labels’.

Additional kwargs: hold=[True|False] overrides default hold state