[R] How to catch data from the different dataframes and lm problem?

Hsin-Ya Lee leeznar at yahoo.com.tw
Mon Dec 31 06:22:53 CET 2007


Dear Richie:

1) I have a mistake in the code that “A.split[[1]][["time"]][i]” should
replace with “A.split[[j]][["time"]][i]”.  The “test” value is “auc” which
is a cumulative rate of change of concentration with respect to time.  

for (j in 1:length(A.split)){
test <- 0
for(i in 2:length(A.split[[j]][["time"]])){
    test[i] <- (A.split[[j]][["time"]][i] - A.split[[j]][["time"]][i-1]) *
(A.split[[j]][["concentration"]][i] - A.split[[j]][["concentration"]][i-1])*
0.5
    test[i]<-test[i]+test[i-1]
 }
output<-data.frame(A.split[[j]][["subject"]],A.split[[j]][["formulation"]],A.split[[j]][["time"]],A.split[[j]][["concentration"]],test)
colnames(output)<-list("subject","formulation","time","concentration","test")
show(output) 
}

subject formulation time   concentration(X) test(Y)
1       1           1    1           0.1  0.00
2       1           1    2          10.0  4.95
3       1           1    3          20.0  9.95
  subject formulation time concentration(X) test(Y)
1       1           2    1            20  0.0
2       1           2    2            25  2.5
3       1           2    3            60  20.0
  subject formulation time concentration(X) test(Y)
1       2           1    1           0.3  0.00
2       2           1    2           2.5  1.10
3       2           1    3           6.0  2.85
  subject formulation time concentration(X) test(Y)
1       2           2    1            35  0.0
2       2           2    2            40  2.5
3       2           2    3            45  5.0

2) Then, I want to pool all "concentration" (X) and pool all "test" (Y) to
perform a 
regression.  For example, I used the “regression” function of Microsoft
Excel 2003 and intercept is -0.01894 and X is 0.185758.  I think that if I
can catch “test” (Y) values and “concentration” (X) values into a dataframe,
then I can use “lm” to fit linear models.  So, how to catch all “test”
values from different dataframes?  Or what should I do? 

Best regards,

Hsin-Ya Lee

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