def test_piecewise_linear_interpolation(self):
# Empty function
f = ContinousPiecewiseLinearFunc()
catched = False
try:
self.assertAlmostEqual(f.interpolate(0), 0, 3)
except:
catched = True
self.assertTrue(catched)
# Single point function
f = ContinousPiecewiseLinearFunc()
f.append(0, 0)
self.assertAlmostEqual(f.interpolate(0), 0, 6)
self.assertAlmostEqual(f.interpolate(-1), 0, 6)
self.assertAlmostEqual(f.interpolate(1), 0, 6)
# A simple well-behaved function
f = ContinousPiecewiseLinearFunc()
f.append(0, 0)
f.append(1, 100)
self.assertAlmostEqual(f.interpolate(-0.000000001), 0, 6)
self.assertAlmostEqual(f.interpolate(0), 0, 6)
self.assertAlmostEqual(f.interpolate(0.000000001), 0, 6)
self.assertAlmostEqual(f.interpolate(0.5), 50.0, 6)
self.assertAlmostEqual(f.interpolate(0.9999999999), 100, 6)
self.assertAlmostEqual(f.interpolate(1.0), 100, 6)
self.assertAlmostEqual(f.interpolate(1.0000000001), 100, 6)
# Function with double-point (infinite derivative)
f = ContinousPiecewiseLinearFunc()
f.append(0, 0)
f.append(1, 0)
f.append(1, 100)
f.append(2, 100)
self.assertAlmostEqual(f.interpolate(0), 0, 6)
self.assertAlmostEqual(f.interpolate(1), 100, 6)
self.assertAlmostEqual(f.interpolate(-1), 0, 6)
# A more complex one
f = ContinousPiecewiseLinearFunc()
f.append(10, 9000)
f.append(20, 10000)
f.append(1000, 10980)
self.assertAlmostEqual(f.interpolate(5), 9000.0, 6)
self.assertAlmostEqual(f.interpolate(15), 9500.0, 6)
self.assertAlmostEqual(f.interpolate(40), 10020.0, 3)
self.assertAlmostEqual(f.interpolate(1010), 10980.0, 3)
def __init__(self, shape):
self._shape = shape
self._cache = _CacheEntry(None)
self._cache_hit = 0
self._cache_miss = 0
if all(pt.shape_dist_traveled != -999999 for pt in shape.points):
self._xdist = ContinousPiecewiseLinearFunc()
else:
self._xdist = None
# Normalize the shape here:
# 1) dist_traveled to meters
# 2) pt_seq to contiguous numbering from 0
ptseq = 0
distance_meters = 0.0
last_pt = None
shape.points.sort(key=lambda p: p.shape_pt_sequence)
for pt in shape.points:
if last_pt is not None:
# Note: we do not use distance cache, as most probably
# many of the points will be different from each other.
distance_meters += orthodromic_distance(last_pt, pt)
last_pt = pt
pt.shape_pt_sequence = ptseq
old_distance = pt.shape_dist_traveled
pt.shape_dist_traveled = distance_meters
# Remember the distance mapping for stop times
if self._xdist:
self._xdist.append(old_distance, pt.shape_dist_traveled)
ptseq += 1
