Douglas Schwarz

Bryan, that's interesting. Back when I first wrote this function, that was not an error, but at some point TMW changed textscan and I didn't notice. Anyway, I just submitted a fix. Thanks for the report!

Paul,

Thank you for your comments. First of all, you should know that the definitions for I and J were specifically requested by users -- they were not included at all in early versions of the program. I have no opinion about them since I don't use them myself. Certainly, backwards compatibility is important so they are not going to change.

I would encourage you to write a simple wrapper function that runs intersections and then converts its outputs into whatever you require. I hesitate to do that for you since I'm not completely sure what it is you need, but feel free to contact me via email if you need help with it.

Doug

Jack,

No, it's not random.

For the NON-ROBUST option:
Number the line segments of your polygon from 1 to N, as defined by the order of the x- and y-coordinates. For each P1P2 line segment, the intersections are found in order of the polygon segments. In other words, if P1P2 crosses polygon segments 12 and 25, the intersection with segment 12 will be first followed by the intersection with segment 25, because 12 < 25.

For the ROBUST option:
Because unique() is run on the intersections, they end up being sorted in increasing order of the x-coordinate (with any tie broken by sorting y).

Doug

Bryan, that's interesting. Back when I first wrote this function, that was not an error, but at some point TMW changed textscan and I didn't notice. Anyway, I just submitted a fix. Thanks for the report!

Excellent work. Saved me a much time and headache with some data analysis over here at NASA. Thank you!