Re: [R] breakpoints and nonlinear regression

2012-01-19 Thread Vito Muggeo (UniPa)
dear Julian, Il 18/01/2012 14.36, crimsonengineer87 ha scritto: Thanks for the comments. Yes, I also had segmented and then I went away from that. I can't remember. I've tried using it but I get some sort of strange error. Here's some code ... it is difficult for me to help you without

Re: [R] breakpoints and nonlinear regression

2012-01-18 Thread crimsonengineer87
Thanks for the comments. Yes, I also had segmented and then I went away from that. I can't remember. I've tried using it but I get some sort of strange error. Here's some code ... pavlu.glm - glm(Na ~ yield, data=pavludata, family=gaussian) pavlu.seg - segmented(pavlu.glm, seg.Z=~yield,

[R] breakpoints and nonlinear regression

2012-01-17 Thread crimsonengineer87
Dear Forum, I have been wracking my head over this problem for the past few days. I have a dataset of (x,y). I have been able to obtain a nonlinear regression line using nls. However, we would like to do some statistical analysis. I would like to obtain a confidence interval for the curve. We

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Kenneth Frost
Hi, Julian- I'm not sure if this will be what you want but you could start by taking a look at: ?predict.nls Ken On 01/17/12, crimsonengineer87 julianjonre...@gmail.com wrote: Dear Forum, I have been wracking my head over this problem for the past few days. I have a dataset of (x,y). I

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Kenneth Frost
Sorry, that wasn't to helpful...I see that the intervals and se.fit argument are currently ignored. On 01/17/12, crimsonengineer87 julianjonre...@gmail.com wrote: Dear Forum, I have been wracking my head over this problem for the past few days. I have a dataset of (x,y). I have been able

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread crimsonengineer87
Hi Ken, Thx for that advice. I took a brief look at it. I already have my curve by just using the curve() function using the parameters a and b given by the nls. Would se.fit and interval have computed the CI? Maybe where I'm confused is at how I can break up my curve into pieces of linear

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Bert Gunter
On Tue, Jan 17, 2012 at 8:06 AM, Kenneth Frost kfr...@wisc.edu wrote: Sorry, that wasn't to helpful...I see that the intervals and se.fit argument are currently ignored. Yes, because the fitted values are nonlinear in the parameters, which makes finding exact confidence regions impossible. I

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Achim Zeileis
On Tue, 17 Jan 2012, crimsonengineer87 wrote: Dear Forum, I have been wracking my head over this problem for the past few days. I have a dataset of (x,y). I have been able to obtain a nonlinear regression line using nls. However, we would like to do some statistical analysis. I would like to

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Achim Zeileis
On Tue, 17 Jan 2012, Bert Gunter wrote: On Tue, Jan 17, 2012 at 8:06 AM, Kenneth Frost kfr...@wisc.edu wrote: Sorry, that wasn't to helpful...I see that the intervals and se.fit argument are currently ignored. Yes, because the fitted values are nonlinear in the parameters, which makes

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread crimsonengineer87
Thanks for the comments everyone. I was hoping to not have to find someone in the stats department ... well, we'll see. So in response to Z's comment ... I have tried breakpoints(Na ~ yield) and I did expect to get something continuous. The idea was to get two or three linear functions making up

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Rolf Turner
In respect of fitting piecewise linear regressions, have you looked at the segmented package? cheers, Rolf Turner On 18/01/12 04:30, crimsonengineer87 wrote: Dear Forum, I have been wracking my head over this problem for the past few days. I have a dataset of (x,y). I have been

Re: [R] breakpoints and nonlinear regression

2012-01-17 Thread Achim Zeileis
On Tue, 17 Jan 2012, crimsonengineer87 wrote: Thanks for the comments everyone. I was hoping to not have to find someone in the stats department ... well, we'll see. So in response to Z's comment ... I have tried breakpoints(Na ~ yield) and I did expect to get something continuous. You