How to check if a line segment is the extension of another?

Question

What if I have 2 line segments that is defined by two starting and ending points such as below:

line segment 1 starts [0,0] and ends at [5,0] another line segment 2 starts at [3,0] and ends at [8,0]

How do I check that line segment 2 extends out of line segment 2 and also if the two line segments aren't necessarily horizontal nor vertical but at a slope? Is there a generalized code for that? Thank you in advance.

This is not a python question, rather it is all simple math. — Malik Brahimi, May 19 '15 at 10:42
If they overlap, one end point of line A must lie on line B and vice versa. — tobias_k, May 19 '15 at 10:44
@tobias_k: Not vice versa. One of the line segments might be completely contained in the other. — cfh, May 19 '15 at 10:45
@cfh But then it is not "the extension" of the other. (At least by my intuitive understanding of "extending" something the extension should not be entirely contained within the thing it extends) — tobias_k, May 19 '15 at 10:46
I've already handled when one segment is inside another but haven't known how to see the case that I asked above. — Mahmoud Ayman, May 19 '15 at 10:47

score 0 · Answer 1 · answered May 19 '15 at 10:49

Use scipy linear regressions to save yourself some pretty obvious but lengthy code:

x1 = np.array([0, 5])
y1 = np.array([0, 0])

x2 = np.array([3, 0])
y2 = np.array([8, 0])

data1 = scipy.stats.linregress(x1, y1)
data2 = scipy.stats.linregress(x2, y2)

m1, b1 = data1[:2] # slope and intercept of 1st line
m2, b2 = data2[:2] # slope and intercept of 2nd line

if m1 == m2 and b1 == b2:
    print 'These are extensions'

How to check if a line segment is the extension of another?

1 Answers1