matplotlib畫箭頭

一、總結

一句話總結：

ax.annotate("", xy=(1-0.1, 6), xytext=(1-0.1, 9),arrowprops=dict(arrowstyle="<->"))

arrowstyle="<->" 表示雙向箭頭

 

 

二、matplotlib畫箭頭

import numpy as np
import matplotlib.pyplot as plt
from scipy.interpolate import make_interp_spline
# 設置matplotlib庫字體的非襯線字體為黑體
plt.rcParams["font.sans-serif"]=["SimHei"]
# 設置matplotlib庫字體族為非襯線字體
plt.rcParams["font.family"]="sans-serif"

fig, ax = plt.subplots()
# 取消邊框
for key, spine in ax.spines.items():
    # 'left', 'right', 'bottom', 'top'
    if key == 'left' or key == 'right':
        spine.set_visible(False)
plt.xticks(np.arange(6), ('','t1', 't2', 't3', 't4', 't5'))
plt.yticks([])

# 上部分圖
x_mean=[0,2,3,4,7]
x_list=[1,2,3,4,5]

x=np.array(x_list)
y=np.array([19,14,16,18,13])
y_mean=np.mean(y).repeat(5)
#plt.plot(x,y,'ro')
plt.plot(x,y,color='red', marker='o', linestyle='dashed',linewidth=0, markersize=12)
plt.plot(x_mean,y_mean,'k--')
x_smooth = np.linspace(x.min(),x.max(),300) #300 represents number of points to make between T.min and T.max
y_smooth = make_interp_spline(x, y)(x_smooth)
plt.plot(x_smooth,y_smooth,'r--')
plt.text(-1.7,np.mean(y),r'X均值'+r'$:\mu_x$', fontdict={'size':16,'color':'r'})

# 下部分圖
y2=np.array([9,4,6,8,3])
y2_mean=np.mean(y2).repeat(5)
#plt.plot(x,y,'ro')
plt.plot(x,y2,color='red', marker='o', linestyle='dashed',linewidth=0, markersize=12)
plt.plot(x_mean,y2_mean,'k--')
x2_smooth = np.linspace(x.min(),x.max(),300) #300 represents number of points to make between T.min and T.max
y_smooth = make_interp_spline(x, y2)(x2_smooth)
plt.plot(x_smooth,y_smooth,'r--')
plt.text(-1.7,np.mean(y2),r'Y均值'+r'$:\mu_y$', fontdict={'size':16,'color':'r'})

# 畫虛線
d_y=np.linspace(0,22,10)
for i in range(len(x_list)):
    d_x=np.array([x_list[i] for j in range(10)])
    plt.plot(d_x,d_y,'g--',linewidth=0.5)

ax.annotate("", xy=(1-0.1, 6), xytext=(1-0.1, 9),arrowprops=dict(arrowstyle="<->"))
plt.text(-0.2,7,r'$Y_1-\mu_y$', fontdict={'size':12,'color':'b'})
ax.annotate("", xy=(1-0.1, 16), xytext=(1-0.1, 19),arrowprops=dict(arrowstyle="<->"))
plt.text(-0.2,17,r'$X_1-\mu_x$', fontdict={'size':12,'color':'b'})
ax.annotate("", xy=(2-0.1, 6), xytext=(2-0.1, 4),arrowprops=dict(arrowstyle="<->"))
plt.text(1.5,7,r'$Y_2-\mu_y$', fontdict={'size':12,'color':'b'})
ax.annotate("", xy=(2-0.1, 16), xytext=(2-0.1, 14),arrowprops=dict(arrowstyle="<->"))
plt.text(1.5,17,r'$X_2-\mu_x$', fontdict={'size':12,'color':'b'})
# t時刻標注
plt.show()

 

 

 

 

 

三、matplotlib畫箭頭

轉自或參考：

import numpy as np
import matplotlib.pyplot as plt



def drawArrow1(A, B):
    '''
    Draws arrow on specified axis from (x, y) to (x + dx, y + dy). 
    Uses FancyArrow patch to construct the arrow.

    The resulting arrow is affected by the axes aspect ratio and limits. 
    This may produce an arrow whose head is not square with its stem. 
    To create an arrow whose head is square with its stem, use annotate() for example:
    Example:
        ax.annotate("", xy=(0.5, 0.5), xytext=(0, 0),
        arrowprops=dict(arrowstyle="->"))
    '''
    fig = plt.figure()
    ax = fig.add_subplot(121)
    # fc: filling color
    # ec: edge color
    ax.arrow(A[0], A[1], B[0]-A[0], B[1]-A[1],
             length_includes_head=True,# 增加的長度包含箭頭部分
             head_width=0.25, head_length=0.5, fc='r', ec='b')
    # 注意： 默認顯示范圍[0,1][0,1],需要單獨設置圖形范圍，以便顯示箭頭
    ax.set_xlim(0,5)
    ax.set_ylim(0,5)
    ax.grid()
    ax.set_aspect('equal') #x軸y軸等比例
    # Example:
    ax = fig.add_subplot(122)
    ax.annotate("", xy=(B[0], B[1]), xytext=(A[0], A[1]),arrowprops=dict(arrowstyle="->"))
    ax.set_xlim(0,5)
    ax.set_ylim(0,5)
    ax.grid()
    ax.set_aspect('equal') #x軸y軸等比例
    plt.show()
    plt.tight_layout()
    #保存圖片，通過pad_inches控制多余邊緣空白
    # plt.savefig('arrow.png', transparent = True, bbox_inches = 'tight', pad_inches = 0.25) 

#%%
a = np.array([1,2])
b = np.array([3,4])
drawArrow1(a,b)