Markers on a matplotlib plot

[Mark Lawrence]

On 17/10/2013 02:31, Brandon La Porte wrote:
> 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
>

Fine, if you need more help I'll try but I'm no matplotlib expert, your 
best bet is still its user mailing list.

Slight aside would you please read and action this link 
https://wiki.python.org/moin/GoogleGroupsPython, a quick glance above 
will tell you why, thanks :)

-- 
Roses are red,
Violets are blue,
Most poems rhyme,
But this one doesn't.

Mark Lawrence