matplotlib作圖之註釋

不寫python的日子每天都覺得沒啥意思，重新搞起~

matplotlib中圖的註釋

直接上代碼看例子：

import numpy as np

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111)

#[0,5]區間，間隔0.01

t = np.arange(0.0, 5.0, 0.01)

s = np.cos(2*np.pi*t)

#lw線條寬度2

ax.plot(t, s, lw=2)

"""

'local max'爲註釋的文本

箭頭指向座標系中的點(2, 1)

註釋文本位於座標系點(3, 1.5)

箭頭樣式arrowprops=dict(facecolor='black', shrink=0.05)

"""

ax.annotate('local max', xy=(2, 1), xytext=(3, 1.5),

            arrowprops=dict(facecolor='black', shrink=0.05))

#y座標軸（-2，2）範圍

ax.set_ylim(-2,2)

#作圖

plt.show()

import numpy as np

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111)

t = np.arange(0.0, 5.0, 0.01)

s = np.cos(2*np.pi*t)

ax.plot(t, s, lw=2)

"""

此處xycoords='data',xytext=(0.8, 0.95), textcoords='axesfraction'

是定義的註釋文本的位置方式。

(0.8, 0.95)表示，註釋文本位於座標系的橫座標的80%，縱座標的95%位置

"""

ax.annotate('local max', xy=(3, 1),  xycoords='data',

            xytext=(0.8, 0.95), textcoords='axes fraction',

            arrowprops=dict(facecolor='black', shrink=0.05),

            horizontalalignment='right', verticalalignment='top'

            )

ax.set_ylim(-2,2)

plt.show()

import numpy as np

import matplotlib.pyplot as plt

fig = plt.figure()

ax = fig.add_subplot(111, polar=True)

r = np.arange(0,1,0.001)

theta = 2*2*np.pi*r

ax.plot(theta, r, color='#ee8d18', lw=3)

ind = 800

thisr, thistheta = r[ind], theta[ind]

ax.plot([thistheta], [thisr], 'o')

ax.annotate('a polar annotation',

            xy=(thistheta, thisr),  

            xytext=(0.05, 0.05),   

            #註釋文本位於，相對於figure而言

            textcoords='figure fraction',

            arrowprops=dict(facecolor='black', shrink=0.05),

            #水平對齊方式：左對齊

            horizontalalignment='left',

            #垂直對齊方式：bottom對齊

            verticalalignment='bottom')

plt.show()