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How to create some derived arrow classes with matplotlib and python

Date: 2007-01-03  |   Tags: matplotlib, python
Here is an example of how to create some derived arrow classes with matplotlib and python. The arrow() function in matplotlib accepts origin and delta x and delta y inputs. I changed this to polor coordinates so Arrow2 accepts the x and y coordinates of the origin, the length, and the angle. Then I created 4 classes derived from Arrow2 called ArrowRight, ArrowLeft, ArrowUp, and ArrowDown. These just set the angle for you to 0, 180, 90, and 270 respectively. Notice too that the **kwargs can be passed down so you can still set all the other parameters. 
""" arrow_ex2.py """ 
from pylab import *  

def main(): 
    figure() 
    axes() 
    Arrow2(.5,.5,.2,45) 
    ArrowRight(.5,.5,.2) 
    ArrowLeft(.5,.5,.2) 
    ArrowUp(.5,.5,.2) 
    ArrowDown(.5,.5,.2) 
    show() 

class Arrow2: 
    def __init__(self, x0, y0, length, angle=0.0, color='k', width=0.01, **kwargs):          
        dx = length*cos(angle*pi/180) 
        dy = length*sin(angle*pi/180) 
        arrow (x0, y0, dx, dy, 
               width=width, 
               edgecolor=color,  
               facecolor=color,  
               antialiased=True,  
               head_width=5*width, 
               head_length=7.5*width, 
               **kwargs)

class ArrowRight(Arrow2): 
    def __init__(self, x0, y0, length, **kwargs): 
        Arrow2.__init__(self, x0, y0, length, angle=0.0, **kwargs)

class ArrowLeft(Arrow2): 
    def __init__(self, x0, y0, length, **kwargs): 
        Arrow2.__init__(self, x0, y0, length, angle=180.0, **kwargs)                      

class ArrowUp(Arrow2): 
    def __init__(self, x0, y0, length, **kwargs): 
        Arrow2.__init__(self, x0, y0, length, angle=90.0, **kwargs) 

class ArrowDown(Arrow2): 
    def __init__(self, x0, y0, length, **kwargs): 
        Arrow2.__init__(self, x0, y0, length, angle=270.0, **kwargs) 

if __name__ == "__main__": 
    main()

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