[R] Change the class of columns in a data frame

[Dimitris Rizopoulos]

you can do it like this:

# example data
DF <- data.frame(nominal = rep(2, 5), ordinal = c(1,2,2,1,2))

DF$nominal <- factor(DF$nominal)
DF$ordinal <- ordered(DF$ordinal)
DF
str(DF)


I hope it helps.

Best,
Dimitris


On 11/24/2010 8:27 PM, Άγνωστος μέσα στο πλήθος wrote:
> Hi.
>
> First of all, excuse me if I do any mistakes, but English is not a language
> I use very often.
>
> I have a data frame with numbers. A small part of the data frame is this:
>
>
>    nominal ordinal
>         2       2
>         2       1
>         2       1
>         2       2
>
>
> So, I want to use the gower distance function on these numbers.
>
> Here (
> http://rgm2.lab.nig.ac.jp/RGM2/R_man-2.9.0/library/StatMatch/man/gower.dist.html)
> says that in order to use gower.dist, all nominal variables must be of
> class "factor" and all ordinal variables of class "ordered".
>
> By default, all the columns are of class "integer" and mode "numeric". In
> order to change the class of the columns, i use these commands:
>
>
>> DF=read.table("clipboard",header=TRUE,sep="\t")      *# I select all the
> cells and I copy them to the clipboard. Then R, with this command, reads the
> data from there.*
>
>> MyHeader=names(DF)     *# I save the headers of the data frame to a temp
> matrix*
>
>> for (i in 1:length(DF))  {if (MyHeader[[i]]=="nominal")
> DF[[i]]=as.factor(DF[[i]])}
>
>> for (i in 1:length(DF))  {if (MyHeader[[i]]=="ordinal")
> DF[[i]]=as.ordered(DF[[i]])}        * *
>
>
> The first for/if loop changes the class from integer to factor, which is
> what I want, but the second changes the class of ordinal variables to:
> "ordered" "factor".
>
> I need to change all the columns with the header "ordinal" to "ordered", as
> the gower.dist function says.
>
> Thanks in advance,
> B.T.
>
> 	[[alternative HTML version deleted]]
>
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>

-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
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