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import numpy as np
import time
import datetime
def timeit(func):
def f(*args, **kwargs):
t0 = time.time()
retval = func(*args, **kwargs)
elapsed = time.time() - t0
print '%s elapsed in %s().' % (datetime.timedelta(seconds=elapsed), func.__name__)
return retval
return f
def read_csv(filename):
"""Return an array of comma-separated values from `filename`."""
f = open(filename)
points = []
for line in f:
try:
points.append([float(s) for s in line.split(',')])
except ValueError:
pass
f.close()
return np.array(points)
def offset(points, x):
"""
Return the set of points obtained by offsetting the edges of the profile
created by `points` by an amount `x`.
Args:
- points: array
Array of points which define the 2-D profile to be offset.
- x: float
Distance to offset the profile; a positive `x` value will offset
the profile in the direction of the profile path rotated 90 degrees
clockwise.
"""
points = np.asarray(points)
points = np.array([points[0] - (points[1] - points[0])] + list(points) + [points[-1] - (points[-2] - points[-1])])
offset_points = []
for i in range(1,len(points)-1):
v1 = np.cross(points[i]-points[i-1], (0,0,1))[:2]
v1 /= np.linalg.norm(v1)
v1 *= x
a = points[i-1] + v1
b = points[i] + v1
v2 = np.cross(points[i+1]-points[i], (0,0,1))[:2]
v2 /= np.linalg.norm(v2)
v2 *= x
c = points[i] + v2
d = points[i+1] + v2
m = np.empty((2,2))
m[:,0] = b-a
m[:,1] = c-d
try:
j = np.linalg.solve(m, c-a)[0]
except np.linalg.linalg.LinAlgError as e:
offset_points.append(b)
continue
offset_points.append((a + j*(b-a)))
return np.array(offset_points)
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