R help - Dec 2005 - Maintaining factors when copying from one data frame to another

Greetings all:

OK, this is bugging the @#@%* out of me. I know the answer is simple
and straightforward but for the life of me I cannot find it in the
documentation, in the archives, or in my notes (because I know I've
encountered this in the past). My problem is:

I have a data frame with columns A, B, C, D, and E. A, B, and E are
factors and C and D are numeric. I need a new data frame with just A,
C, and D. When I copy these columns to a new data frame
>newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
all the factor data comes out as levels rather than the original
factors. How do I preserve the factors when I copy from one data frame
to another?


Thanks vary much,
Kurt Wollenberg, Ph.D.
Tufts Center for Vision Research
Tufts-New England Medical Center
750 Washington St #450
Boston, MA 02111
Office: 617-636-9028
Fax: 617-636-8945
email: kurt.wollenberg at gmail dot com

Does newDF <- oldDF[,c("A","C","D")] work?

Kurt Wollenberg wrote:
>Greetings all:
>
>OK, this is bugging the @#@%* out of me. I know the answer is simple
>and straightforward but for the life of me I cannot find it in the
>documentation, in the archives, or in my notes (because I know I've
>encountered this in the past). My problem is:
>
>I have a data frame with columns A, B, C, D, and E. A, B, and E are
>factors and C and D are numeric. I need a new data frame with just A,
>C, and D. When I copy these columns to a new data frame
>
>  
>
>>newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
>>    
>>
>
>all the factor data comes out as levels rather than the original
>factors. How do I preserve the factors when I copy from one data frame
>to another?
>
>
>Thanks vary much,
>Kurt Wollenberg, Ph.D.
>Tufts Center for Vision Research
>Tufts-New England Medical Center
>750 Washington St #450
>Boston, MA 02111
>Office: 617-636-9028
>Fax: 617-636-8945
>email: kurt.wollenberg at gmail dot com
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>
>  
>

-- 
Kevin E. Thorpe
Biostatistician/Trialist, Knowledge Translation Program
Assistant Professor, Department of Public Health Sciences
Faculty of Medicine, University of Toronto
email: kevin.thorpe at utoronto.ca  Tel: 416.946.8081  Fax: 416.946.3297

newDF <- oldDF[,c("A","C","D")]

HTH

Kurt Wollenberg wrote:
>Greetings all:
>
>OK, this is bugging the @#@%* out of me. I know the answer is simple
>and straightforward but for the life of me I cannot find it in the
>documentation, in the archives, or in my notes (because I know I've
>encountered this in the past). My problem is:
>
>I have a data frame with columns A, B, C, D, and E. A, B, and E are
>factors and C and D are numeric. I need a new data frame with just A,
>C, and D. When I copy these columns to a new data frame
>
>  
>
>>newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
>>    
>>
>
>all the factor data comes out as levels rather than the original
>factors. How do I preserve the factors when I copy from one data frame
>to another?
>
>
>Thanks vary much,
>Kurt Wollenberg, Ph.D.
>Tufts Center for Vision Research
>Tufts-New England Medical Center
>750 Washington St #450
>Boston, MA 02111
>Office: 617-636-9028
>Fax: 617-636-8945
>email: kurt.wollenberg at gmail dot com
>
>______________________________________________
>R-help@stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>  
>

-- 
Ferdinand Alimadhi
Programmer / Analyst
Harvard University
The Institute for Quantitative Social Science
(617) 496-0187
falimadhi@latte.harvard.edu
www.iq.harvard.edu


	[[alternative HTML version deleted]]

Kurt Wollenberg wrote:
>Greetings all:
>
>OK, this is bugging the @#@%* out of me. I know the answer is simple
>and straightforward but for the life of me I cannot find it in the
>documentation, in the archives, or in my notes (because I know I've
>encountered this in the past). My problem is:
>
>I have a data frame with columns A, B, C, D, and E. A, B, and E are
>factors and C and D are numeric. I need a new data frame with just A,
>C, and D. When I copy these columns to a new data frame
>
>  
>
>>newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
>>    
>>
>
>all the factor data comes out as levels rather than the original
>factors. How do I preserve the factors when I copy from one data frame
>to another?
>
>  
>
The following may be better:

newDF <- subset(oldDF, select = c(A, C, D))

HTH,
Tobias

On Wed, 7 Dec 2005, Kurt Wollenberg wrote:
> Greetings all:
> 
> OK, this is bugging the @#@%* out of me. I know the answer is simple
> and straightforward but for the life of me I cannot find it in the
> documentation, in the archives, or in my notes (because I know I've
> encountered this in the past). My problem is:
> 
> I have a data frame with columns A, B, C, D, and E. A, B, and E are
> factors and C and D are numeric. I need a new data frame with just A,
> C, and D. When I copy these columns to a new data frame
> 
> >newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
set.seed(1)
oldDF <- data.frame(A=rnorm(5), B=rnorm(5), C=factor(letters[1:5]),
D=rnorm(5))
str(oldDF)
newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
str(newDF) # cbind forces to numeric as a matrix, so avoid it here
newDFa <- data.frame(Aa=oldDF$A, Ca=oldDF$C, Da=oldDF$D)
str(newDFa)

> 
> all the factor data comes out as levels rather than the original
> factors. How do I preserve the factors when I copy from one data frame
> to another?
> 
> 
> Thanks vary much,
> Kurt Wollenberg, Ph.D.
> Tufts Center for Vision Research
> Tufts-New England Medical Center
> 750 Washington St #450
> Boston, MA 02111
> Office: 617-636-9028
> Fax: 617-636-8945
> email: kurt.wollenberg at gmail dot com
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no