TCD@CORNELLA.BITNET (Tim Dorcey) (02/06/90)
I have a client who has a bunch of data arranged according to zip codes. He would like to aggregate the data for a given county (in the state of New York) and plot the results using the map data sets provides with SAS. Does anyone know how to determine what county a zipcode region falls in? Would it be something like x1 < zip code < x2 ==> a certain county or is a look-up table required? Thanks, Tim Dorcey BITNET: TCD@CORNELLA Statistical Software Consultant Internet: TCD@CORNELLA.CIT.CORNELL.EDU Cornell Information Technologies Cornell University Ithaca, NY 14853
PRAHL@MACC.WISC.EDU (Walter Prahl, MACC) (02/07/90)
> I have a client who has a bunch of data arranged according to >zip codes. He would like to aggregate the data for a given county (in the >state of New York) and plot the results using the map data sets provides with >SAS. Does anyone know how to determine what county a zipcode region falls in? >Would it be something like x1 < zip code < x2 ==> a certain county or is a >look-up table required? Thanks, The SAS Institute sells a tape (identified as D103) that cross-references ZIP codes and counties. It is one of the tapes in the Institute's "Data Library Series", which is briefly discussed on page 449 of the Version 5 SAS/Graph manual. I used this tape several years ago to do something like what the client wants to do here. I don't have any of the material in front of me, but I remember finding (to my disappointment) that this is a much more difficult problem than one would like it to be. For starters, realize that the cross-reference from ZIP code to county is not unique: some ZIP codes cross county lines. In fact, believe it or not, even the cross-reference from ZIP code to STATE is not unique! If I remember correctly, the Institute's tape handles this by providing a "primary" county for each ZIP code, and then a "secondary" county. Problem is, in a typical data set there is no easy way to determine whether a given observation is from the primary or the secondary county, when it exists (even though the primary county is, presumably, the most likely). As I remember, there were also various other difficulties. For example, the data on the Institute's tape was several years old, and ZIP codes are surprisingly volatile (the post office reassigns ZIP codes sometimes). Before ordering the tape, you might want to explain these problems to the client. ---------------------------------- Walter Prahl (608) 262-0284 University of Wisconsin -- MACC Internet: prahl@vms.macc.wisc.edu Bitnet: prahl@wiscmacc.bitnet