implement line_intersection

ntrfc/utils/math/vectorcalc.py

@@ -11,7 +11,7 @@ from scipy.spatial.distance import squareform, pdist
 
 import sys
 import math as m
-import scipy
+
 
 def calc_largedistant_idx(x_koords, y_koords):
     """
@@ -231,3 +231,20 @@ def lineseg_dist(p, a, b):
 
     return np.hypot(h, np.linalg.norm(c))
 
+def line_intersection(point_a1, point_a2,
+                      point_b1, point_b2):
+    def det_2d(a, b):
+        return a[0] * b[1] - a[1] * b[0]
+
+    xdiff = (point_a1[0] - point_a2[0], point_b1[0] - point_b2[0])
+    ydiff = (point_a1[1] - point_a2[1], point_b1[1] - point_b2[1])
+
+    div = det_2d(xdiff, ydiff)
+    if div == 0:
+        return None
+
+    d = (det_2d(point_a1, point_a2), det_2d(point_b1, point_b2))
+    x = det_2d(d, xdiff) / div
+    y = det_2d(d, ydiff) / div
+    return x, y
+

tests/test_ntrfc_math.py

@@ -166,3 +166,12 @@ def test_vecAngle():
     b = np.array([0, 1, 0])
     angle = vecAngle(a, b)
     assert angle == np.pi / 2
+
+
+def test_line_intersection():
+    import numpy as np
+    from ntrfc.utils.math.vectorcalc import line_intersection
+
+    intersect = line_intersection((-1,0),(1,0),
+                      (0,-1),(0,1))
+    assert all(intersect==np.array([0,0]))