collapse mulitple columns into one column and generate an index variable

Question

I have three date columns as shown below

       Id Date1       Date2         Date3
       12 2005-12-22  NA            NA
       11 2009-10-11  NA            NA
         


        

Answer 1

You can also use tidyr with a small hack for the id:

library(tidyr)

df[is.na(df)]=''

transform(unite(df, 'Date', Date1:Date3, sep=''), 
          id=ceiling(which(df[-1]!='')/nrow(df)))
#  Id       Date id
#1 12 2005-12-22  1
#2 11 2009-10-11  1
#3 29 2005-04-11  2
#4 45 2008-11-06  2
#5 39 2006-01-02  3
#6 44 2005-04-16  3