R help - Oct 2010 - Empty data frame does not maintain column type

Does anyone know why a data frame created with empty character columns
converts them to integer columns?
> df<-data.frame(a=character(0),b=character(0))
> df<-rbind(df,c("a","a"))
> typeof(df[1,1])
[1] "integer"

AsIs doesn't help:
> df<-data.frame(a=I(character(0)),b=I(character(0)))
> df<-rbind(df,I(c("a","a")))
> typeof(df[1,1])
[1] "integer"

Any suggestions on how to overcome this would be appreciated.

Best wishes,

David

This should do it:

df <- data.frame(a=character(0), b=character(0), stringsAsFactors=F)

because:

typeof(factor(0))

is "integer"

while:

typeof(character(0))

is "character".

Cheers,

Jeff.

On Wed, Oct 6, 2010 at 1:00 PM, N David Brown <hubdave at gmail.com>
wrote:
> Does anyone know why a data frame created with empty character columns
> converts them to integer columns?
>
>> df<-data.frame(a=character(0),b=character(0))
>> df<-rbind(df,c("a","a"))
>> typeof(df[1,1])
> [1] "integer"
>
> AsIs doesn't help:
>
>> df<-data.frame(a=I(character(0)),b=I(character(0)))
>> df<-rbind(df,I(c("a","a")))
>> typeof(df[1,1])
> [1] "integer"
>
> Any suggestions on how to overcome this would be appreciated.
>
> Best wishes,
>
> David
>
> ______________________________________________
> 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.
>

Try this:

df <- data.frame(a=character(0),b=character(0), stringsAsFactors = FALSE)
df[1,] <- c('a', 'a')


On Wed, Oct 6, 2010 at 2:00 PM, N David Brown <hubdave@gmail.com> wrote:
> Does anyone know why a data frame created with empty character columns
> converts them to integer columns?
>
> > df<-data.frame(a=character(0),b=character(0))
> > df<-rbind(df,c("a","a"))
> > typeof(df[1,1])
> [1] "integer"
>
> AsIs doesn't help:
>
> > df<-data.frame(a=I(character(0)),b=I(character(0)))
> > df<-rbind(df,I(c("a","a")))
> > typeof(df[1,1])
> [1] "integer"
>
> Any suggestions on how to overcome this would be appreciated.
>
> Best wishes,
>
> David
>
> ______________________________________________
> R-help@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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

	[[alternative HTML version deleted]]

On Oct 6, 2010, at 1:00 PM, N David Brown wrote:
> Does anyone know why a data frame created with empty character columns
> converts them to integer columns?
Quick answer: it's the strngsAsFactors demon but you have invoked that  
demon twice, Once with data.frame and the second rime with rbind. See  
if this helps:

 > zz <- factor(1:2)
 > typeof(zz)
[1] "integer"  # it's the storage mode

 > df<-data.frame(a=character(0),b=character(0), stringsAsFactors=FALSE)
 > df<-rbind(df,c("a","a"))
 > typeof(df[1,1])
[1] "integer"   # curses, foiled again!

# I tried using strngsAsFactors=FALSE in the rbind call but got garbage:

 > df<-data.frame(a=character(0),b=character(0), stringsAsFactors=FALSE)
 > df<-rbind(df,c("a","a"), stringsAsFactors=FALSE)
 > df
                  c..a....FALSE.. c..a....FALSE...1
1                              a                 a
stringsAsFactors           FALSE             FALSE

# You can set the global stringsAsFactors option since it appears that  
your
# rbind invocation called out the devil again via the rbind.data.frame  
function.
# So this is how you would prevent that behavior:

 > options(stringsAsFactors= FALSE)
 > df<-data.frame(a=character(0),b=character(0))


 > df<-rbind(df,c("a","a"))
 > str(df)
'data.frame':	1 obs. of  2 variables:
  $ X.a.  : chr "a"
  $ X.a..1: chr "a"

-- 
david

>
>> df<-data.frame(a=character(0),b=character(0))
>> df<-rbind(df,c("a","a"))
>> typeof(df[1,1])
> [1] "integer"
>
> AsIs doesn't help:
>
>> df<-data.frame(a=I(character(0)),b=I(character(0)))
>> df<-rbind(df,I(c("a","a")))
>> typeof(df[1,1])
> [1] "integer"
>
> Any suggestions on how to overcome this would be appreciated.
>
> Best wishes,
>
> David
>
> ______________________________________________
> 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