On Sep 29, 2007, at 12:00 AM, Niner wrote: > 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.
In general it is recommended that you provide reproducible code, typically using one of the built in data sets instead of a data set of your own that we have no access to. > # 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? "selfStart" is not an "option", it is a function which you would use to construct the self-starting object. Look at ?selfStart for an example on how to use it. To the best of my understanding, you need to either: 1) provide starting values (what I would recommend, if you have a sense for the range), or 2) provide R with a mechanism for finding the starting values (via constructing a selfStart object, see ?selfStart), or 3) ask R to make very poor guesses, by leaving the start argument empty [ out <- nls(Z~X/(1/(a+b*ev+c*(Y^2))+X/(d+e*exp(f*Y)))-g, data1, trace=T) ] which has a high chance of choking out on you. In an example I just tried, R set all the parameter values to 1. > 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 > [EMAIL PROTECTED] > Haris Skiadas Department of Mathematics and Computer Science Hanover College ______________________________________________ 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.
