On Jul 10, 2010, at 3:17 PM, Bogaso Christofer wrote:
Hi all, please see my code:
library(zoo)
a <- as.yearmon("March-2010", "%B-%Y")
b <- as.yearmon("May-2010", "%B-%Y")
nn <- (b-a)*12 # number of months in between them
nn
[1] 2
as.integer(nn)
[1] 1
What is the correct way to find the number of months between "a" and
"b",
still retaining the INTEGER property?
Not sure what you mean by _retaining_ the integer property since items
of the yearmon class are numeric and are NOT integer. You just
multiplied 2/12 by 12 and got a result that was very slightly less
than 2. There was a thread yesterday where I offered a possible
solution to a request that trunc be slightly less "literal" and allow
(2/12)*12 to be "truncated" to 2.
trnc3 <- function(x) trunc(x+sign(x)* .Machine$double.eps^0.5)
> (b-a)*12 == 2
[1] FALSE
> trnc3((b-a)*12) == 2
[1] TRUE
--
David Winsemius, MD
West Hartford, CT
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