On 8/22/2008 5:34 PM, Ranney, Steven wrote:
> All -
>
> Not sure if this is a real programming question, but here goes:
>
> I have data that looks like
>
> Lake Length Weight
> 1 158 45
> 1 179 70
> 1 200 125
> 1 202 150
> 1 206 145
> 1 209 165
> 1 210 140
> 1 215 175
> 1 216 152
> 1 220 150
> 1 221 165
> ...
>
> where lake goes from 1 - 84 and the number of rows for each lake is variable
> (but > ~20).
> I'm trying to do two things: 1) build a simple linear model of the form
>
> {lm(log10(Weight)~log10(Length)}
>
> for every separate lake in the data set; 2) I'd like to save the intercepts
> and slopes
> from each of these linear regressions into a seperate data frame. Any ideas?
> I think it would
> probably require some kind of 'for' statement, but I'm just not that smart.
Assuming the data are in a data frame called "mydf":
library(nlme)
fm1 <- lmList(log10(Weight)~log10(Length) | Lake, mydf)
coef(fm1)
?lmList
or
t(sapply(split(mydf, mydf$Lake),
function(x){coef(lm(log10(Weight)~log10(Length), data=x))}))
> Thanks for your help,
>
> SR
>
> Steven H. Ranney
> Graduate Research Assistant (Ph.D)
> USGS Montana Cooperative Fishery Research Unit
> Montana State University
> PO Box 173460
> Bozeman, MT 59717-3460
>
> phone: (406) 994-6643
> fax: (406) 994-7479
>
>
> [[alternative HTML version deleted]]
>
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--
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