On Fri, Mar 25, 2011 at 09:14:50PM +0000, Kenn Konstabel wrote: > Dear all, > > I am working with a list of objects each of which contains two POSIXct > objects (say, $Start and $End) and a number of different data in > addition to that. Now an easy way to extract Start times of all object > could be sapply(x, "[", "Start") but this converts them all to > numeric, and so does sapply(x, "[[", "Start"). lapply preserves the > class but is obviously a list rather than an atomic vector but using > unlist is a way of getting rid of the class again. I know the vector > can be converted back using as.POSIXct and that one can set the class > attribute back to "POSIXct" but is there an easier trick that I can't > just figure out? Thanks in advance for any suggestions. > ...
As Gabor Grothendieck pointed out to me when I tried to read a value as
numeric, then force it to POSIXct:
| This line in the code above produces an invalid object:
| class(df$time) <- "POSIXct"
|
| It should be:
| class(df$time) <- c("POSIXct", "POSIXt")
Peace,
david
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