tapply(df$Date, df$SomeFactor, max, simplify=FALSE) works, i.e. it is the unlist() which is losing the class (and perhaps unlist or tapply should be a bit cleverer).
On Mon, 30 Jan 2006, David Randel wrote:
I have a column in a data frame that has a class of "Date" and a mode of "numeric". When I: max(df$Date) My output stays in Date format, i.e. "2006-01-03". However, when I run the following statment: tapply(df$Date, df$SomeFactor, max) my output looks like this: 9129 9493 9861 10226 10591 10956 11320 11687 12052 12417 The returned object is of mode "numeric" and class "array". Each array element is of mode "numeric" and class "numeric". I believe that this is the integer representation of my date. I can't seem to convert it back to a date. How do I get these to be intrepreted as a date instead of a number? Thanks, ~Dave R.
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