On Wed, 2005-03-30 at 11:06 +0100, Steven J. Murdoch wrote: > I would like to draw only the ticks of an axis, but not the axis > itself. I don't think this can be done using axis(), so I am trying to > write a cut-down version in R, which only draws ticks. > > The point at which I am stuck is that the length of a tick is set by > par("tcl") as a fraction of the "height of a line of text". So I would > like to draw a line whose length is also this length. However I cannot > find out how to convert the into units I can pass into lines(). I > thought par("cxy"), but it is too large, as is shown in the code > below. Here the red tick marks are longer than the black ones created > by axis. I have found the relevant function in plot.c: > "GConvertYUnits(Rf_gpptr(dd)->tcl, LINES, NFC, dd);" > but can't find the corresponding R function. > > Can anyone suggest how to find this out, or solve the problem in a > different way? > > # Inward pointing ticks > par("tcl"=1) > > drawticks <- function(at) { > # Start of the ticks > base<-par("usr")[1] > # Length of the ticks > l<-par("cxy")[2]*par("tcl") > for (i in at) { > lines(c(base,base+l),rep(i,2),col="red") > } > } > > # Test plot > plot(c(1,2,3), axes=FALSE) > # Draw ticks in red > drawticks(axTicks(2)) > # Overprint with normal axis > axis(2, axTicks(2))
Steven, Are you trying to do something like this: plot(1:5, axes = FALSE) axis(1, col.axis = "white", tcl = 1) axis(2, col.axis = "white", tcl = 1) or perhaps something like this: plot(1:5, axes = FALSE) axis(1, col.axis = "white", col = "red", tcl = 1) axis(1, col.axis = "white", col = "black", tcl = 0) axis(2, col.axis = "white", col = "red", tcl = 1) axis(2, col.axis = "white", col = "black", tcl = 0) or even something like this: plot(1:5, axes = FALSE) axis(1, col.axis = "white", col = "red", tcl = 1) axis(1, col.axis = "white", col = "white", tcl = 0) axis(2, col.axis = "white", col = "red", tcl = 1) axis(2, col.axis = "white", col = "white", tcl = 0) If you do not want the axis labels, use: plot(1:5, axes = FALSE, ann = FALSE) HTH, Marc Schwartz ______________________________________________ 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