[R] Help with a Loop

[Dimitris Rizopoulos]

look at function lmList() from package 'nlme', e.g.,

# say 'dat' is you data.frame
library(nlme)
fm <- lmList(DrugLevel ~ Day | Participant, data = dat)
fm
summary(fm)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "stathelp" <ebballller1584 at yahoo.com>
To: <r-help at r-project.org>
Sent: Sunday, December 02, 2007 11:33 PM
Subject: [R] Help with a Loop


>
> I am having trouble getting a loop to work for the following 
> problem. Any
> help would be much appreciated. Thanks.
>
> 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
>
> -- 
> View this message in context: 
> http://www.nabble.com/Help-with-a-Loop-tf4933354.html#a14120625
> Sent from the R help mailing list archive at Nabble.com.
>
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