| axTicks {graphics} | R Documentation |
Compute pretty tickmark locations, the same way as R does internally.
This is only non-trivial when log coordinates are active.
By default, gives the at values which
axis(side) would use.
axTicks(side, axp = NULL, usr = NULL, log = NULL)
side |
integer in 1:4, as for axis. |
axp |
numeric vector of length three, defaulting to
par("Zaxp") where “Z” is “x” or
“y” depending on the side argument. |
usr |
numeric vector of length four, defaulting to
par("usr") giving horizontal (‘x’) and vertical
(‘y’) user coordinate limits. |
log |
logical indicating if log coordinates are active; defaults
to par("Zlog") where ‘Z’ is as for the
axp argument above. |
The axp, usr, and log arguments must be consistent
as their default values (the par(..) results) are. If you
specify all three (as non-NULL), the graphics environment is not used
at all. Note that the meaning of axp alters very much when log
is TRUE, see the documentation on par(xaxp=.).
axTicks() can be regarded as an R implementation of the
C function CreateAtVector() in ‘..../src/main/plot.c’
which is called by axis(side,*) when no argument
at is specified.
numeric vector of coordinate values at which axis tickmarks can be
drawn. By default, when only the first argument is specified,
these values should be identical to those that
axis(side) would use or has used.
axis, par. pretty
uses the same algorithm (but independently of the graphics
environment) and has more options. However it is not available for
log = TRUE.
plot(1:7, 10*21:27)
axTicks(1)
axTicks(2)
stopifnot(identical(axTicks(1), axTicks(3)),
identical(axTicks(2), axTicks(4)))
## Show how axTicks() and axis() correspond :
op <- par(mfrow = c(3,1))
for(x in 9999*c(1,2,8)) {
plot(x,9, log = "x")
cat(formatC(par("xaxp"),wid=5),";",T <- axTicks(1),"\n")
rug(T, col="red")
}
par(op)