# Plotting single points on a graph

### Question

I have a violin plot which looks like this:

I want to plot a few individual dots (or lines, crosses, points whichever is easiest) on each x-value, on top of the violins, like this:

How do I go about doing this?

This is the code for making the violin plots (see Violin Plot with Matplotlib)

``````from matplotlib.pyplot import figure, show
from scipy.stats import gaussian_kde
from numpy.random import normal
from numpy import arange

def violin_plot(ax, data, pos, bp=False):
'''
create violin plots on an axis
'''
dist = max(pos)-min(pos)
w = min(0.15*max(dist,1.0),0.5)
for d,p in zip(data,pos):
k = gaussian_kde(d) #calculates the kernel density
m = k.dataset.min() #lower bound of violin
M = k.dataset.max() #upper bound of violin
x = arange(m,M,(M-m)/100.) # support for violin
v = k.evaluate(x) #violin profile (density curve)
v = v/v.max()*w #scaling the violin to the available space
ax.fill_betweenx(x,p,v+p,facecolor='y',alpha=0.3)
ax.fill_betweenx(x,p,-v+p,facecolor='y',alpha=0.3)
if bp:
ax.boxplot(data,notch=1,positions=pos,vert=1)

if __name__=="__main__":
pos = range(5)
data = [normal(size=100) for i in pos]
fig=figure()
violin_plot(ax,data,pos,bp=1)
fig.savefig("violins.gif")
``````
1
10
3/13/2013 10:35:48 AM

Just plot the extra data right after the other plot:

``````from matplotlib.pyplot import figure, show
from scipy.stats import gaussian_kde
from numpy.random import normal
from numpy import arange

def violin_plot(ax, data, pos, bp=False):
'''
create violin plots on an axis
'''
dist = max(pos)-min(pos)
w = min(0.15*max(dist,1.0),0.5)
for d,p in zip(data,pos):
k = gaussian_kde(d) #calculates the kernel density
m = k.dataset.min() #lower bound of violin
M = k.dataset.max() #upper bound of violin
x = arange(m,M,(M-m)/100.) # support for violin
v = k.evaluate(x) #violin profile (density curve)
v = v/v.max()*w #scaling the violin to the available space
ax.fill_betweenx(x,p,v+p,facecolor='y',alpha=0.3)
ax.fill_betweenx(x,p,-v+p,facecolor='y',alpha=0.3)
if bp:
ax.boxplot(data,notch=1,positions=pos,vert=1)

if __name__=="__main__":
pos = range(5)
data = [normal(size=100) for i in pos]
fig=figure()
violin_plot(ax,data,pos,bp=1)

data_x = [0, 1, 2, 2, 3, 4]
data_y = [1.5, 1., 0.7, 2.5, 1, 1.5]
ax.plot(data_x, data_y, 'or')
fig.savefig("violins.gif")
``````

which gives

18
3/13/2013 10:52:17 AM