Folks; I have looked for this subject extensively using all the resources I have
available and could not find a solution; therefore I am sending you this email
seeking for help. I need to solve a discontinuous nonlinear function, but R 2.6
keeps giving me an error. Below is a simple example:
f <- function (t,k,l,u) { r0<-346.1 x<-t-l if (x<0) r0 else
(r0-u)*exp(-k*x)+u }prof1<-read.table("c:\\data.txt",
header=TRUE)results<-nls(y1~f1(t,k,l,u), data=prof1, start=list(k=0.05, l=4,
u=154))
Errors I am getting are:
Error in qr(.swts * attr(rhs, "gradient")) : dims [product 3] do not
match the length of object [10]In addition: Warning messages:1: In if (x < 0)
r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only
the first element will be used2: In if (x < 0) r0 else (r0 - u) * exp(-k * x)
+ u : the condition has length > 1 and only the first element will be used3:
In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length
> 1 and only the first element will be used4: In if (x < 0) r0 else (r0 -
u) * exp(-k * x) + u : the condition has length > 1 and only the first
element will be used5: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u :
the condition has length > 1 and only the first element will be used6: In
.swts * attr(rhs, "gradient") : longer object length is not a
multiple of shorter object length
Data file is this one
t y1
1 0 346.12 3 343.13 6 327.44 12 280.95 18 242.76 24 228.67 36 193.48
48 174.29 72 164.810 96 152.0
Any help?
Thanks a lot
Luis
_________________________________________________________________
PC_MediaCtr_bigscreen_102007
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Luis Orlindo Tedeschi wrote:> Folks; I have looked for this subject extensively using all the resources I have available and could not find a solution; therefore I am sending you this email seeking for help. I need to solve a discontinuous nonlinear function, but R 2.6 keeps giving me an error. Below is a simple example: > > f <- function (t,k,l,u) { r0<-346.1 x<-t-l if (x<0) r0 else (r0-u)*exp(-k*x)+u }prof1<-read.table("c:\\data.txt", header=TRUE)results<-nls(y1~f1(t,k,l,u), data=prof1, start=list(k=0.05, l=4, u=154)) > > Errors I am getting are: > > > Error in qr(.swts * attr(rhs, "gradient")) : dims [product 3] do not match the length of object [10]In addition: Warning messages:1: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used2: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used3: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used4: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used5: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used6: In .swts * attr(rhs, "gradient") : longer object length is not a multiple of shorter object length > Data file is this one > > > t y1 > 1 0 346.12 3 343.13 6 327.44 12 280.95 18 242.76 24 228.67 36 193.48 48 174.29 72 164.810 96 152.0 > > > Any help? > >It would be easier to help if you could persuade your emailer not jumble up you code.... However, I suspect that you need to look into the difference between if and the ifelse() function. -pd> Thanks a lot > > Luis > _________________________________________________________________ > > > PC_MediaCtr_bigscreen_102007 > [[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. >-- O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
Vectorize f using ifelse in place of if:> f <- function (t,k,l,u) {+ r0 <- 346.1 + x<- t-l + ifelse(x < 0, r0, (r0-u)*exp(-k*x)+u) + }> > prof1 = data.frame(+ t = c(0, 3, 6, 12, 18, 24, 36, 48, 72, 96), + y1 = c(346.12, 343.13, 327.44, 280.95, 242.76, 228.67, + 193.48, 174.29, 164.81, 152) + )> > nls(y1 ~ f(t,k,l,u), data=prof1, start=list(k=0.05, l=4, u=154))Nonlinear regression model model: y1 ~ f(t, k, l, u) data: prof1 k l u 0.04981 3.76690 154.04375 residual sum-of-squares: 102.2 Number of iterations to convergence: 3 Achieved convergence tolerance: 2.862e-06>On Nov 30, 2007 9:25 AM, Luis Orlindo Tedeschi <luis.tedeschi at hotmail.com> wrote:> Folks; I have looked for this subject extensively using all the resources I have available and could not find a solution; therefore I am sending you this email seeking for help. I need to solve a discontinuous nonlinear function, but R 2.6 keeps giving me an error. Below is a simple example: > > f <- function (t,k,l,u) { r0<-346.1 x<-t-l if (x<0) r0 else (r0-u)*exp(-k*x)+u }prof1<-read.table("c:\\data.txt", header=TRUE)results<-nls(y1~f1(t,k,l,u), data=prof1, start=list(k=0.05, l=4, u=154)) > > Errors I am getting are: > > > Error in qr(.swts * attr(rhs, "gradient")) : dims [product 3] do not match the length of object [10]In addition: Warning messages:1: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used2: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used3: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used4: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used5: In if (x < 0) r0 else (r0 - u) * exp(-k * x) + u : the condition has length > 1 and only the first element will be used6: In .swts * attr(rhs, "gradient") : longer object length is not a multiple of shorter object length > Data file is this one > > > t y1 > 1 0 346.12 3 343.13 6 327.44 12 280.95 18 242.76 24 228.67 36 193.48 48 174.29 72 164.810 96 152.0 > > > Any help? > > Thanks a lot > > Luis > _________________________________________________________________ > > > PC_MediaCtr_bigscreen_102007 > [[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. >