[R] [r] regression coefficient for different factors
Dimitri Liakhovitski
dimitri.liakhovitski at gmail.com
Fri May 20 19:04:41 CEST 2011
I think you don't need to write "temp.data$a ~ temp.data$b" just "a ~ b"
On Fri, May 20, 2011 at 11:45 AM, Francesco Nutini
<nutini.francesco at gmail.com> wrote:
> Please forgive me for all these questions Dimitri...
>
> I'm running these input:
>
> mylist<-NULL #in order to hold my input
> for(i in levels(mydataset$c)) { temp.data<-mydataset [mydataset$c %in% i]
> mylist[[i]]<- lm(temp.data$a ~ temp.data$b , data=temp.data) }
>
>
> That's the erros returns
> Error in `[.data.frame`(mydataset, niger$site %in% i) :
> "undefined columns selected"
>
>
>
>> Date: Fri, 20 May 2011 10:01:39 -0400
>> Subject: Re: [R] [r] regression coefficient for different factors
>> From: dimitri.liakhovitski at gmail.com
>> To: nutini.francesco at gmail.com
>> CC: rbaer at atsu.edu; r-help at r-project.org
>>
>> First you have to create something (e.g., a list) that holds your output:
>>
>> mylist<-NULL
>>
>> Then you loop through the levels of c and run a regression of a onto b
>> (no need to include c anymore because c will have zero variance within
>> each level of c):
>> for(i in levels(c)){
>> temp.data<-mydataset[mydataset$c %in% i]
>> mylist[[i]]<-lm(a ~ b, data=temp.data)
>> }
>>
>> Once you are done - you can write another loop (this time across all
>> elements of mylist - that will have as many elements as there are
>> levels in c) and extract the coefficients.
>> Dimitri
>>
>>
>> On Fri, May 20, 2011 at 9:57 AM, Francesco Nutini
>> <nutini.francesco at gmail.com> wrote:
>> > Yes Dimitri that's what I mean!
>> > Something like this?
>> >
>> > for(i in levels(c)) { lm(a ~ b * c , data=mydataset)}
>> >
>> > And what about to see the output?
>> >
>> > Thanks!
>> >
>> >> Date: Fri, 20 May 2011 09:46:08 -0400
>> >> Subject: Re: [R] [r] regression coefficient for different factors
>> >> From: dimitri.liakhovitski at gmail.com
>> >> To: nutini.francesco at gmail.com
>> >> CC: rbaer at atsu.edu; r-help at r-project.org
>> >>
>> >> Francesco, do you just want a separate regression for each level of
>> >> your factor c?
>> >> You could write a loop - looping through levels of c:
>> >>
>> >> for(i in levels(c)){
>> >> select your data here and write a regression formula
>> >> }
>> >>
>> >> On Fri, May 20, 2011 at 9:39 AM, Francesco Nutini
>> >> <nutini.francesco at gmail.com> wrote:
>> >> >
>> >> > Thanks for your reply,
>> >> >
>> >> > ?summary produce a multiple r2.
>> >> > My dataset il similar to this one:
>> >> >
>> >> >> a b c
>> >> >> 1 -1.4805676 0.9729927 x
>> >> >> 2 1.5771695 0.2172974 x
>> >> >> 3 -0.9567445 0.5205087 x
>> >> >> 4 -0.9200052 0.8279428 z
>> >> >> 5 -1.9976421 0.9641110 z
>> >> >> 6 -0.2722960 0.6318801 y
>> >> >
>> >> > So, I would like to know the r2 for a~b for every factors levels.
>> >> > Off course I can made the regression separately for every factors,
>> >> > but
>> >> > my dataset have 68 factors...
>> >> >
>> >> > ----------
>> >> > Francesco Nutini
>> >> > PhD student
>> >> > CNR-IREA (Institute for Electromagnetic Sensing of the Environment)
>> >> > Milano, Italy
>> >> >
>> >> > > From: rbaer at atsu.edu
>> >> >> To: nutini.francesco at gmail.com; r-help at r-project.org
>> >> >> Subject: Re: [R] [r] regression coefficient for different factors
>> >> >> Date: Fri, 20 May 2011 08:07:59 -0500
>> >> >>
>> >> >> ?summary
>> >> >>
>> >> >> produces r^2 in 2nd to last line, as in,
>> >> >> > set.seed(12); a=rnorm(100); b = runif(100); c = factor(rep(c('No',
>> >> >> > 'Yes'),50)); df = data.frame(a,b,c)
>> >> >> > head(df)
>> >> >> a b c
>> >> >> 1 -1.4805676 0.9729927 No
>> >> >> 2 1.5771695 0.2172974 Yes
>> >> >> 3 -0.9567445 0.5205087 No
>> >> >> 4 -0.9200052 0.8279428 Yes
>> >> >> 5 -1.9976421 0.9641110 No
>> >> >> 6 -0.2722960 0.6318801 Yes
>> >> >> > mod = lm(a ~ b*c)
>> >> >> > summary(mod)
>> >> >>
>> >> >> Call:
>> >> >> lm(formula = a ~ b * c)
>> >> >>
>> >> >> Residuals:
>> >> >> Min 1Q Median 3Q Max
>> >> >> -1.8196 -0.4754 -0.0246 0.5585 2.0941
>> >> >>
>> >> >> Coefficients:
>> >> >> Estimate Std. Error t value Pr(>|t|)
>> >> >> (Intercept) 0.2293 0.2314 0.991 0.324
>> >> >> b -0.4226 0.3885 -1.088 0.280
>> >> >> cYes 0.1578 0.3202 0.493 0.623
>> >> >> b:cYes -0.5878 0.5621 -1.046 0.298
>> >> >>
>> >> >> Residual standard error: 0.8455 on 96 degrees of freedom
>> >> >> Multiple R-squared: 0.07385, Adjusted R-squared: 0.04491
>> >> >> F-statistic: 2.552 on 3 and 96 DF, p-value: 0.0601
>> >> >>
>> >> >> ------------------------------------------
>> >> >> Robert W. Baer, Ph.D.
>> >> >> Professor of Physiology
>> >> >> Kirksville College of Osteopathic Medicine
>> >> >> A. T. Still University of Health Sciences
>> >> >> 800 W. Jefferson St.
>> >> >> Kirksville, MO 63501
>> >> >> 660-626-2322
>> >> >> FAX 660-626-2965
>> >> >>
>> >> >>
>> >> >> --------------------------------------------------
>> >> >> From: "Francesco Nutini" <nutini.francesco at gmail.com>
>> >> >> Sent: Friday, May 20, 2011 4:17 AM
>> >> >> To: "[R] help" <r-help at r-project.org>
>> >> >> Subject: [R] [r] regression coefficient for different factors
>> >> >>
>> >> >> >
>> >> >> > Dear R-helpers,
>> >> >> >
>> >> >> > In my dataset I have two continuous variable (A and B) and one
>> >> >> > factor.
>> >> >> > I'm investigating the regression between the two variables usign
>> >> >> > the
>> >> >> > command
>> >> >> > lm(A ~ B, ...)
>> >> >> > but now I want to know the regression coefficient (r2) of A vs. B
>> >> >> > for
>> >> >> > every factors.
>> >> >> > I know that I can obtain this information with excel, but the
>> >> >> > factor
>> >> >> > have
>> >> >> > 68 levels...maybe [r] have a useful command.
>> >> >> >
>> >> >> > Thanks,
>> >> >> >
>> >> >> > Francesco Nutini
>> >> >> >
>> >> >> > [[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.
>> >> >> >
>> >> >
>> >> > [[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.
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> Dimitri Liakhovitski
>> >> Ninah Consulting
>> >> www.ninah.com
>> >
>>
>>
>>
>> --
>> Dimitri Liakhovitski
>> Ninah Consulting
>> www.ninah.com
>
--
Dimitri Liakhovitski
Ninah Consulting
www.ninah.com
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