on 08/04/2008 07:40 PM Etienne Bellemare Racine wrote:
Hi all,
Given a string list,
> paste("A",1:5,sep="")
[1] "A1" "A2" "A3" "A4" "A5"
I would like to create an empty data frame using that list as the
header, so I can access my data frame column using,
> df [ list [ i ] ]
Anyone ?
Thanks,
Etienne
You don't indicate how you might want the column classes to be defined, but:
Cols <- paste("A", 1:5, sep="")
> Cols
[1] "A1" "A2" "A3" "A4" "A5"
DF <- read.table(textConnection(""), col.names = Cols)
> DF
[1] A1 A2 A3 A4 A5
<0 rows> (or 0-length row.names)
> str(DF)
'data.frame': 0 obs. of 5 variables:
$ A1: logi
$ A2: logi
$ A3: logi
$ A4: logi
$ A5: logi
Or, as an example of using 'colClasses':
DF <- read.table(textConnection(""), col.names = Cols,
colClasses = "character")
> str(DF)
'data.frame': 0 obs. of 5 variables:
$ A1: chr
$ A2: chr
$ A3: chr
$ A4: chr
$ A5: chr
Note from the "Value" section of ?read.table:
Empty input is an error unless col.names is specified, when a 0-row data
frame is returned: similarly giving just a header line if header = TRUE
results in a 0-row data frame. Note that in either case tthe columns
will logical unless colClasses was supplied.
In this case, I am supplying an empty value using textConnection() in
place of the typical source file name.
HTH,
Marc Schwartz
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