merge date vectors inside a data frame

Question

I have a data structure df with some date vectors, one thou five, like this,

df <- structure(list(one.date = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, "2012-09-23", "2012-09-23", NA, NA, NA, NA, NA, NA, NA, NA, NA), two.date = c(NA, "2012-11-13", NA, "2012-11-19", NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, "2012-09-24", NA, NA, NA), three.date = c(NA, NA, "2012-11-19", NA, NA, NA, NA, NA, "2012-09-22", NA, NA, NA, NA, NA, NA, NA, NA, "2012-09-24", NA, NA), four.date = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, "2012-09-02", "2012-09-10","2012-09-23", NA, NA, NA, NA, NA, NA), five.date = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, "2012-09-24", "2014-09-09", NA, NA, NA, NA)), .Names = c("one.date", "two.date", "three.date", "four.date", "five.date"), row.names = c(NA, 20L), class = "data.frame")
# > df
     one.date   two.date three.date  four.date  five.date
1        <NA>       <NA>       <NA>       <NA>       <NA>
2        <NA> 2012-11-13       <NA>       <NA>       <NA>
3        <NA>       <NA> 2012-11-19       <NA>       <NA>
4        <NA> 2012-11-19       <NA>       <NA>       <NA>
5        <NA>       <NA>       <NA>       <NA>       <NA>
6        <NA>       <NA>       <NA>       <NA>       <NA>
7        <NA>       <NA>       <NA>       <NA>       <NA>
8        <NA>       <NA>       <NA>       <NA>       <NA>
9        <NA>       <NA> 2012-09-22       <NA>       <NA>
10 2012-09-23       <NA>       <NA>       <NA>       <NA>
11 2012-09-23       <NA>       <NA>       <NA>       <NA>
12       <NA>       <NA>       <NA> 2012-09-02       <NA>
13       <NA>       <NA>       <NA> 2012-09-10       <NA>
14       <NA>       <NA>       <NA> 2012-09-23       <NA>
15       <NA>       <NA>       <NA>       <NA> 2012-09-24
16       <NA>       <NA>       <NA>       <NA> 2014-09-09
17       <NA> 2012-09-24       <NA>       <NA>       <NA>
18       <NA>       <NA> 2012-09-24       <NA>       <NA>
19       <NA>       <NA>       <NA>       <NA>       <NA>
20       <NA>       <NA>       <NA>       <NA>       <NA>

Now, I would like to combine, or merge, them into one vector. Like this,

            date  one.date   two.date three.date  four.date  five.date
  1        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  2  2012-11-13       <NA> 2012-11-13       <NA>       <NA>       <NA>
  3  2012-11-19       <NA>       <NA> 2012-11-19       <NA>       <NA>
  4  2012-11-19       <NA> 2012-11-19       <NA>       <NA>       <NA>
  5        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  6        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  7        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  8        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  9  2012-09-22       <NA>       <NA> 2012-09-22       <NA>       <NA>
  10 2012-09-23 2012-09-23       <NA>       <NA>       <NA>       <NA>
  11 2012-09-23 2012-09-23       <NA>       <NA>       <NA>       <NA>
  12 2012-09-02       <NA>       <NA>       <NA> 2012-09-02       <NA>
  13 2012-09-10       <NA>       <NA>       <NA> 2012-09-10       <NA>
  14 2012-09-23       <NA>       <NA>       <NA> 2012-09-23       <NA>
  15 2012-09-24       <NA>       <NA>       <NA>       <NA> 2012-09-24
  16 2014-09-09       <NA>       <NA>       <NA>       <NA> 2014-09-09
  17 2012-09-24       <NA> 2012-09-24       <NA>       <NA>       <NA>
  18 2012-09-24       <NA>       <NA> 2012-09-24       <NA>       <NA>
  19       <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
  20       <NA>       <NA>       <NA>       <NA>       <NA>       <NA>

Any help would be appreciated.

Answer 1

I'm assuming that there is at most 1 non-NA entry per row:

as.vector(apply(df,1,function(x) ifelse(all(is.na(x)),NA,x[!is.na(x)])))
 [1] NA           "2012-11-13" "2012-11-19" "2012-11-19" NA          
 [6] NA           NA           NA           "2012-09-22" "2012-09-23"
[11] "2012-09-23" "2012-09-02" "2012-09-10" "2012-09-23" "2012-09-24"
[16] "2014-09-09" "2012-09-24" "2012-09-24" NA           NA

Or to have it as a factor as you have in your original data:

cbind(list(date=as.factor(apply(df,1,function(x) ifelse(all(is.na(x)),NA,x[!is.na(x)])))),df)
         date   one.date   two.date three.date  four.date  five.date
1        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
2  2012-11-13       <NA> 2012-11-13       <NA>       <NA>       <NA>
3  2012-11-19       <NA>       <NA> 2012-11-19       <NA>       <NA>
4  2012-11-19       <NA> 2012-11-19       <NA>       <NA>       <NA>
5        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
6        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
7        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
8        <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
9  2012-09-22       <NA>       <NA> 2012-09-22       <NA>       <NA>
10 2012-09-23 2012-09-23       <NA>       <NA>       <NA>       <NA>
11 2012-09-23 2012-09-23       <NA>       <NA>       <NA>       <NA>
12 2012-09-02       <NA>       <NA>       <NA> 2012-09-02       <NA>
13 2012-09-10       <NA>       <NA>       <NA> 2012-09-10       <NA>
14 2012-09-23       <NA>       <NA>       <NA> 2012-09-23       <NA>
15 2012-09-24       <NA>       <NA>       <NA>       <NA> 2012-09-24
16 2014-09-09       <NA>       <NA>       <NA>       <NA> 2014-09-09
17 2012-09-24       <NA> 2012-09-24       <NA>       <NA>       <NA>
18 2012-09-24       <NA>       <NA> 2012-09-24       <NA>       <NA>
19       <NA>       <NA>       <NA>       <NA>       <NA>       <NA>
20       <NA>       <NA>       <NA>       <NA>       <NA>       <NA>

Answer 2

df$onedate <- apply(df, 1, function(x) head(x[!is.na(x)], 1) )

I put the head( ., 1) in to handle cases where there might be more than one date.