[R] Create data frame from header only

[Prof Brian Ripley]

On Mon, 4 Aug 2008, Etienne B. Racine wrote:

>
> Even if it's not so elegant, I will bind it in a function, so I don't have to
> bother with that anymore. I think there should be a simple function in R to
> initialize an empty data frame. From what I've read, it is a recurrent
> question on that list.

Not from what I have seen.  But it is easy with data.frame

colname.list <- paste("A",1:5,sep="") # note this is not a list.
cols <- lapply(colname.list, function(x) numeric(0))
names(cols) <- colname.list
do.call("data.frame", cols)

>
> #Create an empty data frame from a header list
> empty.df<- function(header){
> 	df<-data.frame(matrix(matrix(rep(1,length(header)),1),1))
>  	colnames(df)<-header
> 	return(df[NULL,])
> }
>
> # Usage
> new.df <- empty.df(paste("A",1:5,sep=""))
>> new.df
> [1] A1 A2 A3 A4 A5
> <0 rows> (or 0-length row.names)
>
> Thanks again,
> Etienne
>
>
> milton ruser wrote:
>>
>> Hi Etienne
>>
>> It is not so elegant, bu I think that work.
>>
>>
>> colname.list<-paste("A",1:5,sep="")
>>
>> df<-data.frame(matrix(matrix(rep(1,length(colname.list)),1),1))
>> df
>> colnames(df)<-colname.list
>> df
>>
>> df<-df[-1,]
>> df
>>
>> Cheers,
>>
>>
>> Miltinho Astronauta
>> Brazil
>>
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595