I've never had any issues with the way that plot.POSIXct chooses the
labels of the date axis before, but in this particular case it's output
is a little confusing.
plot(seq(as.POSIXct("1997-10-01"),length.out=108,by="month"),rnorm(108))
This command produces a chart with every x tick mark labeled as "Jan
01".
I can replicate this chart by adding the format string "%b %d".
plot(seq(as.POSIXct("1997-10-01"),length.out=108,by="month"),rnorm(108),
format="%b-%d")
My contention is that plot.POSIXct should choose "%Y" in this case,
which would show unique labels rather than repeated labels.
plot(seq(as.POSIXct("1997-10-01"),length.out=108,by="month"),rnorm(108),
format="%Y")
Now, just looking at axis.POSIXct it seems that the terminal condition
of this if/else sequence sets format to "%b %d":
}
else if (d < 7 * 60 * 60 * 24) {
sc <- 60 * 60 * 24
if (missing(format))
format <- "%a"
}
else {
sc <- 60 * 60 * 24
if (missing(format))
format <- "%b %d" #****** here
}
when the second set of if conditions fires up, format has already bet
set, so the missing(format) test fails here and does not set the format
to %Y:
else {
class(z) <- c("POSIXt", "POSIXct")
zz <- as.POSIXlt(z)
zz$mday <- 1
zz$isdst <- zz$mon <- zz$hour <- zz$min <- zz$sec <- 0
zz$year <- pretty(zz$year)
z <- as.POSIXct(zz)
if (missing(format))
format <- "%Y" #****** here
}
I'm not sure if this is the intended behavior or not. Does anyone else
have any thoughts on this issue?
Thanks,
Whit
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