Thank you Gabor for your quick response, but it didn't solve the issue, I still got the same error message when calling the function. BTW, is there any other way to get the prediction interval of nonlinear regression than using nls2 package? If yes, I might be able to avoid the possible hidden problems.
Thanks, Tianchan -----Original Message----- From: Gabor Grothendieck [mailto:ggrothendi...@gmail.com] Sent: Wednesday, January 02, 2013 2:16 PM To: Tianchan Niu Cc: r-help@r-project.org Subject: Re: [R] Need help with self-defined function to perform nonlinear regression and get prediction interval On Wed, Jan 2, 2013 at 1:23 PM, tn85 <n...@isis.georgetown.edu> wrote: > Dear All, > > I was trying to call a self-defined function that performs nonlinear > regression and gets the corresponding prediction upper limit using > nls2 package. However, weird thing happened. When I called the > function in the main program, an error message "fitted(nlsmodel): > object 'nlsmodel' not found" came up. But when I directly ran the > codes inside the function, no error came up and the codes worked well. > I have never encountered this problem with all the other self-defined > functions, only this one, so I doubt it is caused by something in the nls2 > package. > > I attached my main program and the function as follows. Thank you all > in advance. > > # Main program > rm(list=ls()) > x <- c(0,1,3,4,5,2,10,4,6,8,7) > y <- seq(0,10,1) > ftestnls(x,y) # Call the function > > # function 'ftestnls(v1,v2)' > # v1 <- x > # v2 <- y > ftestnls <- function(v1,v2){ > datalist <- list(v1=v1,v2=v2) > startvalues <- list(a0=v1[1],a1=0,a2=0) > > # Perform nonlinear regression > require(nls2) > nlsmodel <- nls(v1~a0 + a1*v2 + a2 > *sin(2*pi*v2/365.25),data=datalist,start=startvalues, trace=TRUE) > > # Fitted data and prediction interval > fitted <- > predict(as.lm(nlsmodel),se.fit=TRUE,interval="confidence",level=0.95) > uplim <- fitted$fit[,3] > > return(uplim) > } > I was concerned that as.lm does not generalize well and removed it from nls2. You can either use an older version of nls2: http://cran.r-project.org/src/contrib/Archive/nls2/ or source it from the svn repo: library(nls2) source("http://nls2.googlecode.com/svn-history/r8/trunk/R/as.lm.R";) ______________________________________________ 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.
