[Rd] astonishing memory phenomenon
Fri, 11 Feb 2000 14:21:44 +0100
Thanks for the explanation Brian!
> You only have one character data object, of length 0, 4096, 8192,>and lots
of references to it.
> You don't need multiple copies of the same data.
This (definitely clever) behaviour of R makes it more difficult to decide,
HOW to import large amounts of data, if the data type is DATE. Dates could
be imported as CHARACTER or as DOUBLE (chron-objects).
Memory requirements of chron would be approx n*8 Bytes
Memory requirements of character dates like "01/01/2000" would be n*4 + u*10
Memory requirements of character times like "23:03:20" would be n*4 + u*8
Memory requirements of character date-times like "01/01/2000 23:03:20" would
be n*4 + u*19
where n=no of cases and u=no of unique values
Concerning date-times from
n*8 < n*4 + u*19
n/u < 4.75
as a condition for the chron object beeing smaller than a character
representation, thus the answer is: IT DEPENDS.
BTW: Is there any specific reason that currently we cannot have chron
objects as columns of data.frames?
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