[R] surprising dates

[ivo welch]

I wonder if this is an intentional feature or an oversight.  in some
column summaries or in ifelse operations, apparently I am losing the
date property of my vector.

> a <- c(198012, 198101, 198102)
> b <- a*100+31
> c <- as.Date( as.character(b), "%Y%m%d" )

> summary(c)
        Min.      1st Qu.       Median         Mean      3rd Qu.         Max.
"1980-12-31" "1981-01-07" "1981-01-15" "1981-01-15" "1981-01-23" "1981-01-31"
> summary( cbind(1:3, c) )
       V1            c
 Min.   :1.0   Min.   :4017
 1st Qu.:1.5   1st Qu.:4025
 Median :2.0   Median :4032
 Mean   :2.0   Mean   :4032
 3rd Qu.:2.5   3rd Qu.:4040
 Max.   :3.0   Max.   :4048
               NA's   :   1


> d <- a*100+28
> e <- as.Date( as.character(d), "%Y%m%d" )
> e
[1] "1980-12-28" "1981-01-28" "1981-02-28"
> c
[1] "1980-12-31" "1981-01-31" NA
> ifelse( is.na(c), e, c )
[1] 4017 4048 4076   # date property is lost

PS: this time I do not need help.  I can write my code around this.

regards,

/ivo