[R] Non-linear regression/Quantile regression

[despaired]

Hi,

thanks, it works :-)
But where is the difference between demand ~ Time + I(Time^2) and demand ~
poly(Time, 2) ?
Or: How do I have to interpret the results? (I get different results for the
two methods)

Thank you again!


Gabor Grothendieck wrote:
> 
> Those are linear in the coefficients so try these:
> 
> library(quantreg)
> 
> rq1 <- rq(demand ~ Time + I(Time^2), data = BOD, tau= 1:3/4); rq1
> 
> # or
> rq2 <- rq(demand ~ poly(Time, 2), data = BOD, tau = 1:3/4); rq2
> 
> 
> On Tue, Jun 9, 2009 at 10:55 AM, despaired<meyfarth at uni-potsdam.de> wrote:
>>
>> Hi,
>>
>> I'm relatively new to R and need to do a quantile regression. Linear
>> quantile regression works, but for my data I need some quadratic
>> function.
>> So I guess, I have to use a nonlinear quantile regression. I tried the
>> example on the help page for nlrq with my data and it worked. But the
>> example there was with a SSlogis model. Trying to write
>>
>> dat.nlrq <- nlrq(BM ~ I(Regen100^2), data=dat, tau=0.25, trace=TRUE)
>>
>> or
>>
>> dat.nlrq <- nlrq(BM ~ poly(Regen100^2), data=dat, tau=0.25, trace=TRUE)
>>
>> (I don't know the difference) both gave me the following error message:
>>
>> error in getInitial.default(func, data, mCall = as.list(match.call(func,
>>  :
>>  no 'getInitial' method found for "function" objects
>>
>> Looking in getInitial, it must have to do something with the starting
>> parameters or selfStart model. But I have no idea, what this is and how I
>> handle this problem. Can anyone please help?
>>
>> Thanks a lot in advance!
>> --
>> View this message in context:
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>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
> 
> ______________________________________________
> 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.
> 
> 

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