container/restrain_in_sphere.py

## \example container/restrain_in_sphere.py
# This fragment shows how to restrain a set of points stored in a
# SingletonContainer in a sphere of radius 'radius' centered around
# 'center'.

import IMP.example
radius = 10
stiffness = 2
center = IMP.algebra.Vector3D(1, 2, 3)
(m, c) = IMP.example.create_model_and_particles()
ub = IMP.core.HarmonicUpperBound(radius, stiffness)

# Restrain based on the distance to a single point (hence a ball
ss = IMP.core.DistanceToSingletonScore(ub, center)

r = IMP.container.SingletonsRestraint(ss, c)
m.add_restraint(r)
m.evaluate(False)