Hi Mike, you can try using axTicks as in this example (you can also use pretty instead).
Below, instead of a barplot() I have used plot() but with type="h" and lend=3 (see ?par for details on lend) which I have found to be useful at times when making barchart-like plots with time-series. In any case, barplot() or plot(), I hope this illustration will be helpful: # define function to convert numeric to POSIXct # from http://tolstoy.newcastle.edu.au/R/help/04/05/0980.html numToPOSIXct <- function(v) { now <- Sys.time() Epoch <- now - as.numeric(now) Epoch + v } # define example data x <- seq(as.POSIXct("1950-01-01 00:00:00"),as.POSIXct("2000-01-01 00:00:00"),by="year") y <- runif(length(x)) # plot and label axis with with axTicks() plot(x,y,type="h",lwd=3,col=8,xaxt="n",lend=3) axis(1,at=axTicks(1),lab=format(numToPOSIXct(axTicks(1)),"%Y")) --- Mike Prager <[EMAIL PROTECTED]> wrote: > Marc Schwartz <[EMAIL PROTECTED]> wrote: > > > On Tue, 2007-03-20 at 18:04 -0400, Michael H. Prager wrote: > > > I am generating stacked barplots of age-composition of fish populations > > > > (Y) over time (X). As there are many years, not every bars is labeled. > > > > When looking at the plot, it becomes difficult to associate labels with > > > > their bars. > > > > > > We have improved this a bit by using axis() to add a tickmark below > each > > > bar. Can anyone suggest a way to draw ticks ONLY at bars where a tick > > > label is drawn? Or to make such ticks longer than those where there is > > > > no label? > > > > > > This is going into a function, so I'm hoping for a method that doesn't > > > require looking at the plot first. > > > > > > # sample code (simplified) # > > > mp <- barplot(t(N.age), xlab = "Year", axisnames = FALSE) > > > axis(side = 1, at = mp, labels = rownames(N.age), tcl = -0.75) > > > > > > Thanks! > > > > > > Mike Prager > > > NOAA, Beaufort, NC > > > > Mike, > > > > How about something like this: > > > > mp <- barplot(1:50, axisnames = FALSE) > > > > # Create short tick marks at each bar > > axis(1, at = mp, labels = rep("", 50), tcl = -0.25) > > > > # Create longer tick marks every 5 years with labels > > axis(1, at = mp[seq(1, 50, 5)], > > labels = 1900 + seq(0, 45, 5), tcl = -0.75, las = 2, > > cex.axis = 0.75) > > > > > > Just pick which labels you want to be shown (eg. every 5 years) and > > synchronize the values of those with the 'at' argument in axis(). > > > > HTH, > > > > Marc Schwartz > > > > Thanks, Marc, for this solution and thanks equally to Jim Lemon > for a similar idea. This seems promising. Since this is to go > into a function (and should work without intervention), I'll > need to devise an algorithm to decide at what interval the > labels should be plotted. Clearly "axis()" has such an > algorithm. Unfortunately, it reports its result only by placing > the labels. > > Mike > > -- > Mike Prager, NOAA, Beaufort, NC > * Opinions expressed are personal and not represented otherwise. > * Any use of tradenames does not constitute a NOAA endorsement. > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ____________________________________________________________________________________ Expecting? Get great news right away with email Auto-Check. ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
