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Date:   Thu, 17 Jul 2003 08:43:45 -0400
Reply-To:   Eric <eoyount@WARMMAIL.COM>
Sender:   "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:   Eric <eoyount@WARMMAIL.COM>
Organization:   heat email address to reply
Subject:   Re: Use SAS to fit this curve?
Content-Type:   text/plain; charset=us-ascii

Hi Mike,

I would first suggest you ask a statistic

On 16 Jul 03 18:04:50 GMT, rmf4@CDC.GOV (Mike Fay) wrote:

>Hi folks, > >I'm an amateur user of SAS, and even worse with statistics (laugh). >Recently we charted some descriptive data that I'd like to fit to a curve, >but am unsure how to ask SAS to do this. Or more especially, is there a way >to ask SAS to search through the different fit possibilities and report on >which are the best fit? > >The data itself is appended. It shows the number of U.S. hazardous waste >sites at which N or more chemicals are found in an exposure pathway. For >example, the "n_chems = 2, n_sites = 588" observation means that two (or >more) chemicals are found in an exposure pathway at 588 sites. (The >universe N is 1706 -- many sites don't have a single exposure pathway.) >(This data is draft and subject to revision as the generating algorithm is >refined; do not cite or quote.) > >If I play around with several possible fits, such as exponential or >logarithmic, the best R2 is from an exponential fit. But it appears to be >unable to cope with the steep drop-off and then levelling off, even though >the curve seems pretty darn smooth to the eye. In other words, although I >get an R2 of .955 in Excel's very simple "put a fit on this data" >functionality, it obviously misses especially the beginning of the curve. >And I don't know what else to do if Excel's missing it... but I'm willing >to bet SAS (v9) can do a lot more than Excel ;) > >Anyone is also welcome to point out any other math/stats software that >might exist, particularly for the Windows environment. And the simpler >(VERY simple) to operate, the better, lol. > >TIA if you can help! > > Mike, Atlanta > >*** > >input N_Chems N_Sites; > >cards; > > 1 743 > 2 588 > 3 475 > 4 390 > 5 321 > 6 266 > 7 214 > 8 185 > 9 161 > 10 136 > 11 111 > 12 102 > 13 87 > 14 74 > 15 69 > 16 61 > 17 56 > 18 52 > 19 47 > 20 46 > 21 44 > 22 39 > 23 36 > 24 33 > 25 29 > 26 26 > 28 24 > 29 22 > 30 20 > 31 19 > 32 18 > 37 16 > 38 15 > 39 13 > 40 11 > 41 10 > 42 9 > 48 7 > 49 6 > 51 5 > 56 4 > 58 3 > 62 2 > >;


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