Dear all:
I am a new R-user and I have 2 questions about it. 1) I have a dataframe. Based on “formulation” and “subject”, a dataframe is split into 4 dataframes. The example is as follows. Moreover, I want to calculate “test” value for these 4 dataframes. My question is that the “test” values not correct and I do not know where the problem is. 2) There are 12 “test” (y) values from 1). Then, I want to model the relationship between “concentration” (X) and “test” (Y) by fitting the linear regression, such lm(Y~X) and this is my target. I think that if I can catch “test” (Y) values and “concentration” (X) values into a dataframe, then I can carry out regression. So, how to catch all “test” values from different dataframes? Or does anyone have better way to get this target? Example: w<-(c(1,1,1,2,2,2,1,1,1,2,2,2)) y<-(c(1,1,1,1,1,1,2,2,2,2,2,2)) z<-(c(1,2,3,1,2,3,1,2,3,1,2,3)) c<-(c(0.1,10,20,0.3,2.5,6,20,25,60,35,40,45)) df<-data.frame(formulation=y, subject=w, time=z, concentration=c) A.split<-split(df, list(df$formulation, df$subject) ) for (j in 1:length(A.split)){ test <- 0 for(i in 2:length(A.split[[j]][["time"]])){ test[i] <- (A.split[[1]][["time"]][i] - A.split[[1]][["time"]][i-1]) * (A.split[[1]][["concentration"]][i] - A.split[[1]][["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) } Best regards, Hsin-Ya Lee _____________________________________________________________________________________ 馬上體驗全新Yahoo!奇摩電子信箱2.0。 http://tw.mg0.mail.yahoo.com/dc/landing ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.