Arrow class

1.Arrow Class introduction

Arrow3.4.1 Official documents
Here are maplotlib Inheritance graph in Library ：

It can be seen from the picture that ,Arrow Class inherits from Patch Class is the basic parent class , Is specifically responsible for the various attributes and implementation of the arrow . However, the degree of freedom of this class is not very high, and it is impossible to accurately set all the attributes you want to specify , At the same time, keep in mind that the instance of this class is not what we often think arrow Return value of method . He returned to FancyArrow example .

1.1Arrow Class definition

class Arrow(x, 
			y, 
			dx, 
			dy, 
			width=1.0, 
			**kwargs)

Parameter description ：

Parameters 1：x： floating-point , Specifies the end of the arrow X coordinate
Parameters 2：y： floating-point , Specifies the end of the arrow Y coordinate
Parameters 3：dx： floating-point , Specifies the of the arrow X Direction coordinates
Parameters 4：dy： floating-point , Specifies the of the arrow Y Direction coordinates
Parameters 5：width： floating-point , Specifies the scale factor for the width of the arrow , Default head width 0.6, Tail width 0.2
Parameters 6：kwargs： receive Patch attribute ,Patch See the reference link for properties .

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Parameters, ：

1. Arrow Class specifies the arrow from **(x, y) Start , This coordinate is also used as the central coordinate of the tail of the arrow , From this point on , Point to (x + dx, y + dy)** until .
2. width Property specifies the scale , Remember that proportion , Instead of specifying absolute values , It can be understood that the width of the head of the last arrow is 0.6width, The tail width is 0.2width.
3. This kind of instance can be through add_artist perhaps add_patch Method is added to the frame .

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1.2 Example show

1.2.1width Parameter display

We now change width The value of the parameter to see what happens . The example program is as follows ：

import matplotlib.pyplot as plt

plt.rcParams['font.sans-serif'] = ['SimHei']  #  Settings support Chinese 
plt.rcParams['axes.unicode_minus'] = False  #  Set up - Number 

# Initialize frame and data 
figure, [(ax1, ax2), (ax3, ax4)] = plt.subplots(2, 2)
widths = [0.1, 1, 8, 15]

# drawing 
for ax, num, width in zip([ax1, ax2, ax3, ax4], range(4), widths):
    arrow = (plt.Arrow(5, 5, 3, 3, width=width))    #Arrow Create examples 
    ax.add_patch(arrow) # Add instance 
    ax.set_title('width=' + str(width), fontsize=25)
    ax.set_xlabel('X', fontsize=15)
    ax.set_ylabel('Y', fontsize=15)
    ax.autoscale(True)


figure.subplots_adjust(hspace=0.5)
plt.show()

The result is as follows ：

As can be seen from the above figure width Parameters refer to Magnification , Not absolute values , Head 、 The ratio of tail width is constant . Besides, you can see 5, 5) This coordinate corresponds to the midpoint of the tail , and (8, 8) Is the coordinate of the tip of the arrow head .

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1.2.2 obtain 、 Set attribute display

Like the others matplotlib Class instances are consistent , Use get_property(value)、set_property(value), The former is used to get the current property , The latter is used to set the current property .property Represents the name of the property to be set ,value Represents the value to be set . The example program is as follows ：

print('old linewidth=', arrow.get_linewidth())
arrow.set_linewidth(15)
print('new linewidth=', arrow.get_linewidth())

The program runs as follows ：

old linewidth= 1.0
new linewidth= 15.0

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1.2.3 Visual display
Arrow Class has few parameters and is concise ,width The parameters have been introduced , Therefore, I will not repeat too much . Concrete Patch See the reference link for details of the class , This example only shows the passing Patch Visualization of class attribute keyword parameters . The example program is as follows ：

import matplotlib.pyplot as plt

plt.rcParams['font.sans-serif'] = ['SimHei']  #  Settings support Chinese 
plt.rcParams['axes.unicode_minus'] = False  #  Set up - Number 

X = 5   #X coordinate 
Y = 5   #Y coordinate 
dx = 3  #X Coordinate increment 
dy = 3  #Y Coordinate increment 
width = 1.5  # Width ratio 

fig, ax = plt.subplots(3, 3)

# Draw an example standard arrow 
arrow0 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width)
ax[0, 0].add_patch(arrow0)
ax[0, 0].set_title('normal', fontsize=25)

# Change surface color 
arrow1 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, facecolor='#FF0000')
ax[0, 1].add_patch(arrow1)
ax[0, 1].set_title('facecolor=#FF0000', fontsize=25)

# Change the width of the edge line 
arrow2 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, edgecolor='#000000', linewidth=5)
ax[0, 2].add_patch(arrow2)
ax[0, 2].set_title('linewidth=5', fontsize=25)

# Change edge line color 
arrow3 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, edgecolor='#0000FF')
ax[1, 0].add_patch(arrow3)
ax[1, 0].set_title('edgecolor=#0000FF', fontsize=25)

# Change Linetype 
arrow4 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, edgecolor='#000000', linewidth=5, linestyle='--')
ax[1, 1].add_patch(arrow4)
ax[1, 1].set_title('linestyle=--', fontsize=25)

# Change the fill mode 
arrow5 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, fill=False)
ax[1, 2].add_patch(arrow5)
ax[1, 2].set_title('fill=False', fontsize=25)

# Change fill shadow 
arrow6 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, hatch='||')
ax[2, 0].add_patch(arrow6)
ax[2, 0].set_title('hatch=||', fontsize=25)

# Change transparency 
arrow7 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, facecolor='#00FF00', edgecolor='#000000', linewidth=5, alpha=0.1)
ax[2, 1].add_patch(arrow7)
ax[2, 1].set_title('alpha=0.1', fontsize=25)

# Change visibility 
arrow8 = plt.Arrow(x=X, y=Y, dx=dx, dy=dy, width=width, visible=False)
ax[2, 2].add_patch(arrow8)
ax[2, 2].set_title('visible=False', fontsize=25)

for i in range(3):
    for j in range(3):
        ax[i, j].autoscale(True)

fig.subplots_adjust(hspace=0.4, wspace=0.4)

plt.show()

The result is as follows ：

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3. Reference resources

1. Patch Class explanation