Date:         Thu, 3 Feb 2000 18:31:05 +0100
Reply-To:     peter.crawford@DB.COM
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Peter Crawford <peter.crawford@DB.COM>
Subject:      Q: Point in Polygon Test - has anyone seen a Base SAS
              implementation.
Comments: To: finelink@iinet.net.au
Content-type: text/plain; charset=us-ascii

Isn't the algorithm something to do with detecting whether the polygon frontier
passes through X line and Y line an odd number of times or even number of times.
If the point has an odd number of frontiers in all 4 directions the it lies
within. I remember a SAS/Graph map data set routine .........
So it seemed a good time to show those who don't know, just how simple it is to
search for this kind of thing at SI
The default database is v6 usage notes, but more useful for this enquiry is
database TSNOTE which is the full set of technical notes and articles.
So I sent off a search to the SAS Information warehouse, with these results
which will give Bob Whitehead just what he  seeks
>>>>>>>><
I sent to sasnotes@sas.com
database tsnote
search  point inside polygon map
This is a clip from the reply
>>>>>>>>>>>>>>>>>>>>>>>>>>
> database tsnote
> search point inside polygon map

Score Document  Title
-----------------------------------------------------------------------------
1000     ts096  DETERMINING IF A POINT LIES INSIDE A POLYGON - SAS CODE XAMPLE
  11     ts321  SAS Communications(R) Index 1982 - 2Q94

---------------------------------------------------------------------------

To get additional help, send email to sasnotes@sas.com with the word
HELP in the body of the message.

You can retrieve any document by specifying its document name/number.
For example:
     database v6
     get 5371
>>>>>>>>>>>>>>end of clip

All Bob has to do is send to:     sasnotes@sas.com    the message
database tsnote
get  ts096





Datum:         03.02.2000 17:19
An:            SAS-L@listserv.uga.edu




Antwort an:    finelink@iinet.net.au

Betreff:       Q: Point in Polygon Test - has anyone seen a Base SAS
               implementation.
Nachrichtentext:



Hi all,

I thought I'd throw this to the collective intelligence.

I am trying to find a way to implement in Base SAS (maybe GRAPH as well
later) a way
to test if X,Y points in my dataset are inside or outside a polygon.

At this point the best I can say is that the polygon is not necessary a
simple one.

I just need to return a simple flag indicating whether the point is
IN/OUT/BORDER/VERTEX.

I can easily test for the vertex, and I have some ideas for algorithms but I
my geometry is a little (lot!) rusty.

Thanks in advance.


Bob Whitehead
Finelink Nominees Pty Ltd
Perth, Western Australia