I am just starting with R and encountered a strange behaviour: when inserting the first row in an empty data frame, the original column names get lost.
example:
a<-data.frame(one = numeric(0), two = numeric(0))
a
#[1] one two
#<0 rows> (or 0-length row.names)
names(a)
#[1] "one" "two"
a<-rbind(a, c(5,6))
a
# X5 X6
#1 5 6
names(a)
#[1] "X5" "X6"
As you can see, the column names one and two were replaced by X5 and X6.
Could somebody please tell me why this happens and is there a right way to do this without losing column names?
A shotgun solution would be to save the names in an auxiliary vector and then add them back when finished working on the data frame.
Thanks
Context:
I created a function which gathers some data and adds them as a new row to a data frame received as a parameter. I create the data frame, iterate through my data sources, passing the data.frame to each function call to be filled up with its results.
The rbind help pages specifies that :
For ‘cbind’ (‘rbind’), vectors of zero length (including ‘NULL’) are ignored unless the result would have zero rows (columns), for S compatibility. (Zero-extent matrices do not occur in S3 and are not ignored in R.)
So, in fact, a is ignored in your rbind instruction. Not totally ignored, it seems, because as it is a data frame the rbind function is called as rbind.data.frame :
rbind.data.frame(c(5,6))
# X5 X6
#1 5 6
Maybe one way to insert the row could be :
a[nrow(a)+1,] <- c(5,6)
a
# one two
#1 5 6
But there may be a better way to do it depending on your code.