[R] [r] regression coefficient for different factors

David Winsemius dwinsemius at comcast.net
Sat May 21 01:15:07 CEST 2011 

On May 20, 2011, at 11:45 AM, Francesco Nutini 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]

Actually looking at that the second time makes me think you might  
solve the problem with a single comma.

> 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"

First look:
It's possible to create factors defined that have levels with no  
entries. Did you do some sub setting? Maybe you need to skip the  
levels argument and instead use unique(mydataset$c), Hard to say  
without your example  ... which you are requested in the Posting  
Guide ... to post .


>
>
>
>> 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
> 		 	   		
> 	[[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.

David Winsemius, MD
West Hartford, CT

More information about the R-help mailing list