Odp: Help with a Loop

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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Odp: Help with a Loop

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