[R-Forge #5437] By operations with factors

[arunsrinivasan]

Submitted by: Christophe Dervieux; Assigned to: Arun ; R-Forge link

Hi,

I have updated data.table package to 1.9.2 recently from 1.8.10 and I found errors on my previous code.

See reproductible example below:

On 1.8.10 :

DT <- data.table(X = factor(2006:2012), Y = rep(1:7, 2))
DT[, Z := paste(X, .N, sep = " - "), by = list(X)][]

       X     Y        Z
 1: 2006 1 2006 - 2
 2: 2007 2 2007 - 2
 3: 2008 3 2008 - 2
 4: 2009 4 2009 - 2
 5: 2010 5 2010 - 2
 6: 2011 6 2011 - 2
 7: 2012 7 2012 - 2
 8: 2006 1 2006 - 2
 9: 2007 2 2007 - 2
10: 2008 3 2008 - 2
11: 2009 4 2009 - 2
12: 2010 5 2010 - 2
13: 2011 6 2011 - 2
14: 2012 7 2012 - 2

In column Z, I get the level of the factor column X
pasted with count '.N' as expected

However, in the 1.9.2, with same code :

DT<-data.table(X=factor(2006:2012),Y=rep(1:7,2))
DT[,Z:=paste(X,.N,sep=" - "),by=list(X)][]

        X     Y  Z
 1: 2006 1 1 - 2
 2: 2007 2 2 - 2
 3: 2008 3 3 - 2
 4: 2009 4 4 - 2
 5: 2010 5 5 - 2
 6: 2011 6 6 - 2
 7: 2012 7 7 - 2
 8: 2006 1 1 - 2
 9: 2007 2 2 - 2
10: 2008 3 3 - 2
11: 2009 4 4 - 2
12: 2010 5 5 - 2
13: 2011 6 6 - 2
14: 2012 7 7 - 2

as results, I do not get levels of factor column X but the numeric values associated with the level.

is this working normally? Why has it changed? Is that a bug?

I use this kind of procedure to make labels for ggplot. All my previous code is not working anymore. It's kind of annoying.

Thanks

Christophe