Markers on a matplotlib plot

[Brandon La Porte]

On Wednesday, 16 October 2013 18:31:09 UTC-4, Mark Lawrence  wrote:
> On 16/10/2013 22:34, Brandon La Porte wrote:
> 
> > 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.
> 
> >
> 
> 
> 
> If this matplotlib.pyplot.text described here 
> 
> http://matplotlib.org/api/pyplot_api.html isn't any good I suggest you 
> 
> ask on the dedicated matplotlib users mailing list see 
> 
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> 
> 
> 
> -- 
> 
> Roses are red,
> 
> Violets are blue,
> 
> Most poems rhyme,
> 
> But this one doesn't.
> 
> 
> 
> Mark Lawrence

Hi Mark

Thanks for the quick reply.  I went through the documentation briefly and made some changes.

from matplotlib import pyplot as plt

q1 = 2.0
q2 = 4.0
q3 = 5.0
q4 = 10.0

p1 = 20
p2 = 40
price = range(0,51)
qlist1 = [x/q1 for x in price]
qlist2 = [x/q2 for x in price]
qlist3 = [x/q3 for x in price]
qlist4 = [x/q4 for x in price]


plt.plot(qlist1,price,'b',qlist2,price,'g',qlist3,price,'r', qlist4, price, 'y' )
plt.plot(p1/q1,p1,'ko', p1/q2, p1, 'ko', p1/q3,p1, 'ko', p1/q4, p1, 'ko')
plt.plot(p2/q1,p2,'ks', p2/q2, p2, 'ks', p2/q3,p2, 'ks', p2/q4, p2, 'ks')

plt.title('Supply Curve')
plt.xlabel('Quantity Supplied (Thousands per month)')
plt.ylabel('Price ($)')
plt.legend(('p = 2Qs', 'p = 4Qs', 'p = 5Qs', 'p = 10Qs'), loc=4)

plt.grid()
plt.show()


I'm sure there is a better or more "Pythonic" way to do this, and I still need to figure out how to label the individual points.  Again thanks for the links, and I'll update this post when I figure it out.

Thanks
Brandon