Hi,

     I am a student of Earthquake Engineering, and am new to R.  
Currently I try to run nonlinear regression analysis by R. My data  
has three variables: X, Y, and Z. Z is a function of (X, Y). My R  
script is as below.


rm(list=ls())
# read in data
Alldata <- read.table("~/Documents/R/Wu_data.dat", header=TRUE)
# assign variables
Z <- Wu[[1]]     # N1,60
X <- Wu[[2]]   # CSR
Y <- Wu[[3]]    # ev, %

# set the data frame
data1<- data.frame(cbind(N,CSR,ev))

# call nls funciton
out <- nls(Z~X/(1/(a+b*ev+c*(Y^2))+X/(d+e*exp(f*Y)))-g, data1,  
selfStart, trace=T)


In total there are 59 sets of (X,Y,Z). When I run this script, I got  
the error message as:

parameters without starting value in 'data': a, b, d, e, f, g


I don't know what this means. Besides, I use "selfStart" option, such  
that the nls is supposed to run by finding the initial values of  
(a,b,c,d,e,f,g) itself. Why the nls asks me to give the starting values?

What should I do next? Does anyone can explain the meaning of the  
error message?
Any comment is appreciated. Thanks a lot.


Regards,


Niner
----------------------------------------------------
Niner, Seattle
ninerdummy@gmail.com




	[[alternative HTML version deleted]]

