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
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David Winsemius, MD
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
