Markers on a matplotlib plot

[Piet van Oostrum]

Brandon La Porte <laporte.brandon at gmail.com> writes:

> I have the following code to make a plot of 4 different supply curves (economics).
>
>
> from matplotlib import pyplot as plt
>
> price = range(0,51)
> q1 = [x/2.0 for x in price]
> q2 = [x/4.0 for x in price]
> q3 = [x/5.0 for x in price]
> q4 = [x/10.0 for x in price]
>
> markers_on = [20, 40]
>
> plt.plot(q1,price,'b',q2,price,'g',q3,price,'r', q4, price, 'y' )
> plt.title('Supply Curve')
> plt.xlabel('Quantity Supplied (Thousands per month')
> plt.ylabel('Price ($)')
> #plt.legend(('Kd = %d'%kd, 'Kd = %d'%kd2, 'Kd = %d'% kd3, 'Step'), loc=4)
> plt.legend(('p = 2Qs', 'p = 4Qs', 'p = 5Qs', 'p = 10Qs'), loc=4)
>
> plt.grid()
> plt.show()
>
> I would like to place markers on the 4 curves when the price is equal to $20 label it A, and when the price is equal to $40 and label it B.  Does anyone know how I can accomplish this.

Something like:

plt.plot(20,40, 'bo')
plt.annotate('B', (20,40), xytext=(-10,10), textcoords='offset points')

Of course you should write a loop to calculate the x, y points, and use the proper colors.

-- 
Piet van Oostrum <piet at vanoostrum.org>
WWW: http://pietvanoostrum.com/
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