[R] Odp: Help with a Loop

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 02.12.2007 23:33:47:

> 
> I am having trouble getting a loop to work for the following problem. 
Any
> help would be much appreciated. Thanks.

Lets try it without loop.

Does this

lapply(split(data[,4:3], data$Participant), function(x) coef(lm(x)))

give you results you want?

If yes, just put it in some object e.g. lll <- and 

do.call(rbind, lll)

gives you a table output.

Regards
Petr


> 
> I need to find the slope and intercept from the linear regression of 
Drug
> Level on Day by Participant. There are a total of 37 Participants. I 
need to
> store the Participant, Label, Slope, and Intercept in a new data frame. 
> 
> 
> This data is ordered by Participant number 37 total participants. A 
sample
> of the data is given below. 
> 
> 
> Label Participant Day DrugLevel 
> 17      0       1  15 1.84179 
> 121     0       1   5 2.10772 
> 147     0       1   7 3.00658 
> 152     0       1  11 2.91729 
> 250     0       1  10 2.75816 
> 289     0       1  13 3.20468 
> 321     0       1   6 2.43389 
> 362     0       1  12 2.77770 
> 433     0       1   9 3.03167 
> 469     0       1   8 2.97613 
> 475     0       1  14 2.86934 
> 70      0       2  13 0.68022 
> 210     0       2   8 1.41767 
> 243     0       2  11 1.28867 
> 246     0       2   9 1.53601 
> 247     0       2   6 1.64863 
> 280     0       2   5 1.19795 
> 310     0       2  12 1.24440 
> 343     0       2  10 1.18929 
> 413     0       2   7 1.57207 
> 41      0       3   7 1.87884 
> 74      0       3   8 1.82477 
> 100     0       3   5 2.09422 
> 133     0       3   6 1.91853 
> 134     0       3  12 0.90422 
> 149     0       3  11 1.38232 
> 172     0       3  10 1.55323 
> 216     0       3   9 1.24088 
> 65      0       4   8 2.49412 
> 69      0       4   5 1.79840 
> 
> This is my thought process of what the loop needs to do but I cant get 
the
> correct loop. 
> 
> X1=Day[Participant=="1"]
> Y1=DrugLevel[Participant=="1"]
> 
> Coeffs=function(X1,Y1)
> {
> lmfirst=lm(Y1~X1)
> lmfirst$coefficients
> }
> 
> Coeffs(X1,Y1)
> 
> # output slope and intercept here
> # do same for the next participant
> 
> X2=Day[Participant=="2"]
> Y2=DrugLevel[Participant=="2"]
> 
> Coeffs=function(X2,Y2)
> {
> lmfirst=lm(Y2~X2)
> lmfirst$coefficients
> }
> 
> Coeffs(X2,Y2)
> 
> # output slope and intercept here
> # do same for the next participant
> 
> X3=Day[Participant=="3"]
> Y3=DrugLevel[Participant=="3"]
> 
> Coeffs=function(X3,Y3)
> {
> lmfirst=lm(Y3~X3)
> lmfirst$coefficients
> }
> 
> Coeffs(X3,Y3)
> 
> # output slope and intercept here
> # do same for the next participant
> 
> # etc for the rest of the participants
> 
> # any ideas? 
> 
> # thanks 
> 
> -- 
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> tf4933354.html#a14120625
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