I am trying to figure out how to use ggplot2.  I would like to do the below
with ggplot, but I can not figure out how.  The data provided is a subset of
a much larger data set, but these data are the data necessary to make the
plot.  I think I would rather have the colors become symbols, and I do know
how to do that in lattice, but here is a quick and dirty version.
thanks

r <-(structure(list(TSS = c(2.8, 8.4, 11, 1.3, 4.2, 2, 3.4, 14, 8.2,
3.1, 1.4, 0.9, 0.5, 6.1, 9.2, 0.6, 1, 11, 2.4, 1.2, 1.3, 1.3,
0, 1.8, 8, 11, 11, 8.5, 8.5, 1.8, 13, 4.4, 1.4, 2.1, 0.5, 25,
25, 9.3, 6.1, 1.6, 1.5, 19, 19, 24, 9.6, 1.8, 1.4, 1), GPP = c(1.213695235,
3.817313822, 1.267930498, 10.45692825, 3.268295623, 3.505286001,
4.468225245, 0.915653726, 1.635617261, 3.726133898, 1.363453706,
13.99650967, 1.581182762, 0.417618143, 0.741080504, 1.366790205,
0.969326797, 0.412440872, 1.780215366, 3.515743675, 8.248491445,
0.125726306, 13.95880794, 4.850627229, -0.438311644, 1.537773727,
1.537773727, 3.249103284, 3.249103284, 2.470317011, 0.768531626,
2.633107621, 3.113199095, 0.773824094, 3.208461305, 0.680150068,
0.680150068, 0.026385752, 0.369310858, 8.049276658, 7.487378383,
0.950072035, 0.950072035, 0.763580377, 0.333244629, 5.475999014,
9.235631398, 2.587682905), RiverMile = c(148L, 179L, 185L, 202L,
179L, 185L, 190L, 119L, 148L, 179L, 185L, 202L, 215L, 119L, 202L,
198L, 215L, 148L, 198L, 190L, 202L, 215L, 198L, 198L, 215L, 148L,
148L, 202L, 202L, 215L, 119L, 179L, 185L, 190L, 198L, 61L, 61L,
119L, 148L, 202L, 202L, 61L, 61L, 119L, 148L, 185L, 202L, 215L
)), .Names = c("TSS", "GPP", "RiverMile"), class = "data.frame", row.names =
c(12L,
13L, 14L, 19L, 25L, 26L, 28L, 34L, 35L, 36L, 37L, 42L, 44L, 58L,
75L, 85L, 88L, 91L, 97L, 107L, 142L, 144L, 155L, 166L, 169L,
185L, 186L, 201L, 202L, 207L, 219L, 221L, 222L, 224L, 226L, 230L,
231L, 250L, 251L, 258L, 283L, 287L, 288L, 303L, 304L, 306L, 311L,
313L)))

library(lattice)
z <- nls(GPP~(a/(TSS+b)), start=c(a=0.01, b=0.01), data=r)
f <- seq(-1, 29, length=100)
y <- coef(z)["a"]/(f+coef(z)["b"])
xyplot(GPP~TSS, data=r, xlim=c(-0.5, 29), groups=RiverMile ,auto.key=TRUE ,
pch=20 ,panel=function(...)
 {panel.xyplot(...)
 llines(f, y)
}
)


-- 
Stephen Sefick
Research Scientist
Southeastern Natural Sciences Academy

Let's not spend our time and resources thinking about things that are so
little or so large that all they really do for us is puff us up and make us
feel like gods.  We are mammals, and have not exhausted the annoying little
problems of being mammals.

-K. Mullis

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