matplotlib--添加图例和注解

# coding: utf-8
import matplotlib.pyplot as plt
import numpy as np
x1 = np.random.normal(30, 3, 100)
x2 = np.random.normal(20, 2, 100)
x3 = np.random.normal(10, 3, 100)

# 随机正态分布生成x1、x2、x3，并为每个plot指定一个字符串标签
plt.plot(x1, label="plot")
plt.plot(x2, label="plot2")
plt.plot(x3, label="plot3")

# 设置loc参数确定图例框的位置
# 设置列数为nloc=3，指定边框的（bbox_to_anchor）的起始位置为（0.0,1.02），设置宽度为1，高度为0.102，注意这些值都是基于归一化坐标系。参数mode可以设置为None或者expand，当为expand时，图例框会水平的扩展至整个坐标轴区域。参数borderaxespad指定了坐标轴和图例边界之间的间距。

plt.legend(bbox_to_anchor=(0., 1.02, 1., .102), loc=3,
       ncol=3, mode="expand", borderaxespad=0.)

# 进行备注
plt.annotate("Important value", (55,20), xycoords='data',
         xytext=(5, 38),
         arrowprops=dict(arrowstyle='->'))
plt.show()

 

plt.annotate()函数解析:

# plt.annotate()函数用于标注文字

plt.annotate(s='str',
	xy=(x,y) ,
	xytext=(l1,l2) ,
	...
)

参数解释:

s 为注释文本内容

xy 为被注释的坐标点

xytext 为注释文字的坐标位置

xycoords 参数如下:

    figure points：图左下角的点
    figure pixels：图左下角的像素
    figure fraction：图的左下部分
    axes points：坐标轴左下角的点
    axes pixels：坐标轴左下角的像素
    axes fraction：左下轴的分数
    data：使用被注释对象的坐标系统(默认)
    polar(theta,r)：if not native ‘data’ coordinates t

weight 设置字体线型

    {‘ultralight’, ‘light’, ‘normal’, ‘regular’, ‘book’, ‘medium’, ‘roman’, ‘semibold’, ‘demibold’, ‘demi’, ‘bold’, ‘heavy’, ‘extra bold’, ‘black’}

color 设置字体颜色

    {‘b’, ‘g’, ‘r’, ‘c’, ‘m’, ‘y’, ‘k’, ‘w’}
    ‘black’,'red’等

    [0,1]之间的浮点型数据
    RGB或者RGBA, 如: (0.1, 0.2, 0.5)、(0.1, 0.2, 0.5, 0.3)等

arrowprops #箭头参数,参数类型为字典dict

    width：箭头的宽度(以点为单位)
    headwidth：箭头底部以点为单位的宽度
    headlength：箭头的长度(以点为单位)
    shrink：总长度的一部分，从两端“收缩”
    facecolor：箭头颜色

bbox给标题增加外框 ，常用参数如下：

    boxstyle：方框外形
    facecolor：(简写fc)背景颜色
    edgecolor：(简写ec)边框线条颜色
    edgewidth：边框线条大小

# coding: utf-8
import matplotlib.pyplot as plt
import numpy as np

def test1():
    x = np.arange(0, 50, 5)
    print(x)
    y = x * x
    plt.plot(x, y, marker="o")
    for xy in zip(x,y):
        plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(2, 4), textcoords='offset points')
    plt.show()

# test1()

def test2():
    x = np.arange(0,50, 5)
    y = x * x

    plt.plot(x, y, marker='o')
    # weight:增加字体线型
    for xy in zip(x, y):
        plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(-20, 10), textcoords='offset points', weight='heavy')
    plt.show()
# test2()

def test3():
    x = np.arange(0,50,5)
    y = x * x
    plt.plot(x, y, marker='o')
    # 增加字体的颜色
    for xy in zip(x, y):
        plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(-20, 10), textcoords='offset points', color='y', weight='heavy')
    plt.show()

# test3()

def test4():
    x = np.arange(0, 50, 10)
    y = x * x
    plt.plot(x, y, marker='o')
    # 增加箭头
    for xy in zip(x, y):
        plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(-20, 10), textcoords='offset points', color='y', weight='heavy',
                     arrowprops=dict(facecolor="y", headlength=10, headwidth=10, width=20))
    plt.show()

# test4()

def test5():
    x = np.arange(0, 50, 10)
    y = x * x
    plt.plot(x, y, marker='o')
    # 增加标题外框
    for xy in zip(x, y):
        plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(-20, 10), textcoords='offset points',color='y', weight='heavy',
                     arrowprops=dict(facecolor="y", headlength=10, headwidth=10, width=20),
                     bbox=dict(boxstyle='round,pad=0.5', fc='yellow', ec='k', lw=1, alpha=0.5))
    plt.show()

# test5()

def test6():
    x = np.arange(0, 50, 10)
    y = x * x
    plt.plot(x, y, marker='o')
    # 增加箭头指示
    for xy in zip(x, y):
        # plt.annotate("(%s,%s)" % xy, xy=xy, xytext=(-20, 10), textcoords='offset points', color='y', weight='heavy',
        #              arrowprops=dict(facecolor="y", headlength=10, headwidth=10, width=20),
        #              bbox=dict(boxstyle='round,pad=0.5', fc='yellow', ec='k', lw=1, alpha=0.5))
        plt.annotate('local max', xy=(5, 25), xytext=(20, 25), arrowprops=dict(facecolor='red', shrink=0.05))
    plt.show()

# test6()