## Monday, February 22, 2010

### Replot the Poisson example with Python

I realized that I used R for the plot of the Poisson distribution from the other day, and I decided to redo it with matplotlib.

This might be a first, since I finally figured out how to set the axis limits. I still have had another problem, I would like to plot the lines after the points, but matplotlib does it how it wants, I guess. It doesn't matter which order the `plot` and `scatter` calls are in, the points get plotted last. Maybe I'll ask on SO.

[Those guys know everything: the answer is, you just set the zorder. Here is a link to the example code.]

 `import mathimport matplotlib.pyplot as pltdef poisson(m): def f(k): e = math.e**(-m) f = math.factorial(k) g = m**k return g*e/f return fR = range(20)L = list()means = (1,2,4,10)for m in means: f = poisson(m) L.append([f(k) for k in R])colors = ['r','g','b','purple']for c,P in zip(colors,L): plt.plot(R,P,zorder=1,color='0.2',lw=1.5) plt.scatter(R,P,zorder=2,s=150,color=c) ax = plt.axes()ax.set_xlim(-0.5,20)ax.set_ylim(-0.01,0.4)plt.savefig('example.png')`