Greets, I'm trying to learn to use nls and was running the example code for an exponential model:> x <- -(1:100)/10 > y <- 100 + 10 * exp(x / 2) + rnorm(x)/10 > nlmod <- nls(y ~ Const + A * exp(B * x))Error in B * x : non-numeric argument to binary operator In addition: Warning message: In nls(y ~ Const + A * exp(B * x)) : No starting values specified for some parameters. Initializing ‘Const’ to '1.'. Consider specifying 'start' or using a selfStart model Presumably, the code should work if it is part of an example on the help page. In perusing various help forums for similar problems, it also appears that others believe this syntax should work in the model formula. Any ideas? Perhaps also, a pointer to a comprehensive and correct document that details model formulae syntax if someone has one? Thanks & Best Regards, Steven [[alternative HTML version deleted]]
On Thu, Apr 25, 2013 at 7:16 PM, Steven LeBlanc <oreslag at gmail.com> wrote:> Greets, > > I'm trying to learn to use nls and was running the example code for an exponential model: > >> x <- -(1:100)/10 >> y <- 100 + 10 * exp(x / 2) + rnorm(x)/10 >> nlmod <- nls(y ~ Const + A * exp(B * x)) > Error in B * x : non-numeric argument to binary operator > In addition: Warning message: > In nls(y ~ Const + A * exp(B * x)) : > No starting values specified for some parameters. > Initializing ?Const? to '1.'. > Consider specifying 'start' or using a selfStart model > > Presumably, the code should work if it is part of an example on the help page. In perusing various help forums for similar problems, it also appears that others believe this syntax should work in the model formula. > > Any ideas? >Try running in a clean session. Having B <- "X" in your workspace would cause such an error. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com
Hi
Try
x <- -(1:100)/10
set.seed(1)
y <- 100 + 10 * exp(x / 2) + rnorm(x)/10
short cut to starting values
lm(log(y) ~-log(x+10))
Call:
lm(formula = log(y) ~ -log(x + 10))
Coefficients:
(Intercept)
4.624
nlmod <- nls(y ~ A + B * exp(C * x), start=list(A=90, B=5,C=0.1))
Formula: y ~ A + B * exp(C * x)
Parameters:
Estimate Std. Error t value Pr(>|t|)
A 100.009079 0.017797 5619.4 <2e-16
B 9.999993 0.042718 234.1 <2e-16
C 0.499529 0.004495 111.1 <2e-16
Residual standard error: 0.09073 on 97 degrees of freedom
Number of iterations to convergence: 5
Achieved convergence tolerance: 0.00000002475
I will leave you to plot the results as a check
Duncan
Duncan Mackay
Department of Agronomy and Soil Science
University of New England
Armidale NSW 2351
Email: home: mackay at northnet.com.au
At 09:16 26/04/2013, you wrote:>Content-Type: text/plain
>Content-Disposition: inline
>Content-length: 899
>
>Greets,
>
>I'm trying to learn to use nls and was running the example code for
>an exponential model:
>
> > x <- -(1:100)/10
> > y <- 100 + 10 * exp(x / 2) + rnorm(x)/10
> > nlmod <- nls(y ~ Const + A * exp(B * x))
>Error in B * x : non-numeric argument to binary operator
>In addition: Warning message:
>In nls(y ~ Const + A * exp(B * x)) :
> No starting values specified for some parameters.
>Initializing 'Const' to '1.'.
>Consider specifying 'start' or using a selfStart model
>
>Presumably, the code should work if it is part of an example on the
>help page. In perusing various help forums for similar problems, it
>also appears that others believe this syntax should work in the model
formula.
>
>Any ideas?
>
>Perhaps also, a pointer to a comprehensive and correct document that
>details model formulae syntax if someone has one?
>
>Thanks & Best Regards,
>Steven
>
>
>
> [[alternative HTML version deleted]]
>
>
>______________________________________________
>R-help at 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.
On 26/04/2013 00:16, Steven LeBlanc wrote: > Greets, > > I'm trying to learn to use nls and was running the example code for an exponential model: > > <snip> > > Perhaps also, a pointer to a comprehensive and correct document that details model formulae syntax if someone has one? > > Thanks& Best Regards, > Steven > Others have pointed out that the error is probably from an unclean environment. For model formula syntax, see ?nls Under Arguments formula, follow the link to ?formula