That is not the problem, but thanks for your attempted help. I still

don't know what the problem is. Has anyone encountered this while

using "gnls" function in the package "nlme"?

thanks again for any help,

Ravi.

----- Original Message -----

From: Christian Mora <christian_mora@vtr.net>

Date: Wednesday, January 14, 2004 7:15 pm

Subject: RE: [R] Generalized least squares using "gnls" function

Have you tried removing tol=1.e-07 or changing the value considering

that the error is Object "." not found

-----Original Message-----

From: r-help-bounces+christian_mora=vtr.net at stat.math.ethz.ch

[mailto:r-help-bounces+christian_mora=vtr.net at stat.math.ethz.ch] On

Behalf Of Ravi Varadhan

Sent: Wednesday, January 14, 2004 6:11 PM

To: r-help at stat.math.ethz.ch

Subject: [R] Generalized least squares using "gnls" function

Hi:

I have data from an assay in the form of two vectors, one is

response

and the other is a predictor. When I attempt to fit a 5 parameter

logistic model with "nls", I get converged parameter estimates. I

also

get the same answers with "gnls" without specifying the "weights"

argument.

However, when I attempt to use the "gnls" function and try to

estimate

the variance function, as a power function, I get the following

error

message:

start=list(p0=3,p1=1,p2=4,p3=2,p4=1.5),control=gnlsControl(tol=1.e-

07),weights=varPower())

Error in eval(expr, envir, enclos) : Object "." not found

What am I doing wrong here and how can I do a GLS analysis with a

variance function that is estimated from the data?

Here is my data:

36.87912, 26.73256, 25.18681, 17.97674)

3.125000e+01, 1.562500e+01, 7.812500e+00, 3.906250e+00,

1.953125e+00, 9.765625e-01, 4.882813e-01, 2.441406e-01, 1.000000e-03)

thanks for the help,

Ravi.

______________________________________________

R-help at stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help

PLEASE do read the posting guide!

http://www.R-project.org/posting-guide.html

that the error is Object "." not found

-----Original Message-----

From: r-help-bounces+christian_mora=vtr.net at stat.math.ethz.ch

[mailto:r-help-bounces+christian_mora=vtr.net at stat.math.ethz.ch] On

Behalf Of Ravi Varadhan

Sent: Wednesday, January 14, 2004 6:11 PM

To: r-help at stat.math.ethz.ch

Subject: [R] Generalized least squares using "gnls" function

Hi:

I have data from an assay in the form of two vectors, one is

response

and the other is a predictor. When I attempt to fit a 5 parameter

logistic model with "nls", I get converged parameter estimates. I

also

get the same answers with "gnls" without specifying the "weights"

argument.

However, when I attempt to use the "gnls" function and try to

estimate

the variance function, as a power function, I get the following

error

message:

ans51g <- gnls(log(b51) ~ p0 + p1/(1 + exp(-(log(dose)-

p2)/p3))^p4,start=list(p0=3,p1=1,p2=4,p3=2,p4=1.5),control=gnlsControl(tol=1.e-

07),weights=varPower())

Error in eval(expr, envir, enclos) : Object "." not found

What am I doing wrong here and how can I do a GLS analysis with a

variance function that is estimated from the data?

Here is my data:

b51 <- c(17447.60674, 7060.37234, 2872.53012, 796.40426,

454.47222, 260.22340, 120.11905, 83.40196, 51.45745,36.87912, 26.73256, 25.18681, 17.97674)

dose <- c( 1.000000e+04, 1.000000e+03, 2.500000e+02,

6.250000e+01,3.125000e+01, 1.562500e+01, 7.812500e+00, 3.906250e+00,

1.953125e+00, 9.765625e-01, 4.882813e-01, 2.441406e-01, 1.000000e-03)

thanks for the help,

Ravi.

______________________________________________

R-help at stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help

PLEASE do read the posting guide!

http://www.R-project.org/posting-guide.html