Hello Jon Petter, On the surface of it, an uncombine function doesn't seem complicated, but from experience I know there are several things that complicate the solution. MB provides an easy way of extracting the Nth polygon from a region using the ExtractNodes() function. If the begin_node and end_node arguments are both 1, you get the Nth whole polygon. So, this will give you a way of extracting individual polygons, then using the area() function you can perform your "threshold" test. The difficult part comes with determining whether a polygon is an "include" or "exclude". For example, a donut would be 2 polygons, 1 include and 1 exclude. However, not all 2 polygon regions are donuts - you can quite easily have 2 disjoint includes. Also, you can nest inclusion and exclusion zones to create more complex regions. Finally, the first polygon in a region is not guaranteed to be an include. So, even with a simple donut, the hole may be expressed as the first polygon. Regards, Warren Vick Europa Technologies Ltd, U.K. http://www.europa-tech.com > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]On Behalf Of Jon Petter Nielsen > Sent: Monday, December 20, 1999 3:01 PM > To: '[EMAIL PROTECTED]' > Subject: MI Help for MapInfo "Uncombine" ? > > > Hi > I am trying to develop a function to perform "uncombine" on > multi-polygon regions. Then classify them based on area values ("Remove > all smaller than ...") > - Anyone programmed this in MapBasic ? > - Am I able to perform this by looping the polygons using data from > ObjectInfo ? > - How, in general, to detect which polygons are islands and which are > not ? Example : Donut region = 2 polygons. > > Jon Petter Nielsen > InfoWiz AS, Oslo Norway, > [EMAIL PROTECTED] > +47 2296 1563 > ---------------------------------------------------------------------- > To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put > "unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED] > ---------------------------------------------------------------------- To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED]
RE: MI Help for MapInfo "Uncombine" ?
Warren Vick, Europa Technologies Ltd. Mon, 20 Dec 1999 18:19:15 -0800
- MI Help for MapInfo "Uncombine&... Jon Petter Nielsen
- Warren Vick, Europa Technologies Ltd.