[Matplotlib-users] Convex Hull -- Question about Point Size

Lorenzo Isella lorenzo.isella at gmail.com
Fri Apr 15 03:47:18 EDT 2016

```Dear All,
Thanks to what I found here

http://bit.ly/1qJlWkP

I discovered how to plot the convex hull around a set of points
(please have a look at the script pasted at the end of the email).
Everything is almost done,but I have a problem: my "points" are not
really point-like: they are sphere whose radius is 1 and they almost
touch each other.
I do not know how to tune the parameter s so that the radius of the
points is equal to one in the same units in which I measure the
positions of the points themselves.
Any help is appreciated.
Cheers

Lorenzo

################################################################à

import numpy as np
import pylab as pl
import scipy as sp
from scipy.spatial import ConvexHull
from scipy.spatial.distance import euclidean
import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d as a3

cluster_agglomerate=np.array([[ 0.14513811, -0.18930948, -1.44428171],
[ 0.88042945,  1.67057596, -1.45742688],
[-1.66682741, -0.99554261, -1.70267889],
[-0.95535694,  2.3159907 , -1.93637881],
[ 1.09396798,  1.7987614 , -3.44524095],
[-2.63620654,  0.16588691,
-3.02436539],
[ 0.19027056,  2.70740725,  0.11479029],
[ 2.77638842,  1.70535678, -2.10208878],
[-0.09149779, -0.81908733,  2.07425244],
[-0.48408772,  0.96793567,
1.26652603],
[ 0.67499278, -2.5386008 ,  1.39914827],
[ 1.02571108, -1.60932884, -0.34500693],
[ 2.78789155, -1.42050584,  0.59682802],
[-0.14688239, -2.36883246,
3.35177362],
[-1.71507089,  0.19184887,  2.68408562],
[-1.87886026, -1.58255618,  3.97006406],
[ 6.61540229,  1.98324725,  0.82767368],
[ 7.46818823,  3.00950487,
-0.66214223],
[ 4.80777628,  1.97159273,  1.68344958],
[ 6.3548727 ,  2.26459561,  2.92819854],
[ 4.70026626,  0.44618044,  0.3866837 ],
[ 3.44366671,  1.87939977,
-0.2203051 ],
[ 2.92460648,  1.98510457,  2.37510769],
[ 5.07053866, -0.10349542, -1.51041234],
[ 7.21643437, -1.32050186, -0.70707322],
[ 6.93292243,  0.58458074,
-1.2458508 ],
[ 7.84238244, -2.97562362, -1.63914669],
[ 7.43212373,  0.10620418,  0.68315389],
[ 9.59692827, -2.0843759 , -1.26623658],
[ 8.34540867, -1.14927294,
1.95073173],
[ 6.57425162, -2.13797392, -2.94804639],
[ 6.93340304, -4.4591665 , -0.63578546]])

# see http://bit.ly/1qJlWkP

# Generate random points & convex hull
points =  cluster_agglomerate  # np.random.rand(20,3)
print "points are, ", points
hull = ConvexHull(points)
print "I calculated the convex hull"

ax = a3.Axes3D(pl.figure())
facetCol = [1, 0.0, 0.0]

ax.plot_trisurf(points[:,0], points[:,1], points[:,2],
triangles=hull.simplices)

ax.scatter(points[:,0], points[:,1], points[:,2], s=100)

plt.axis('off')
plt.show()

```