[R] Axes Ticks

[Marc Schwartz]

On Thu, 2004-01-22 at 12:32, ivo welch wrote:
> Apologies, basic question on plot.
> 
> 	y <- c(-4,3,-2,1);
> 	x <- c("time 1", "time 2", "time 3", "time 4");
> 	plot(x,y, type="b");
> 
> of course fails.
> 	x <- 1:4
> makes it succeed, but then I have too many ticks on my X axis.  I want 
> exactly 4 tickmarks.  It would also be nicer if I could name the ticks.
> 
> I looked at ?par and Venables&Ripley, and tried the lab and xaxp 
> parameters.  I could not figure out how to use them productively.  could 
> someone please let me know?  help appreciated.  /iaw


Use 'xaxt' in the call to plot() and then use axis() to control the axis
tick marks and labels:

y <- c(-4, 3, -2, 1)
x <- c(1:4)

# Do not plot the x axis
plot(x, y, type = "b", xaxt = "n")

# Now draw the x axis with text labels
axis(1, at = 1:4, labels = paste("Time", 1:4, sep = " "))

See ?par (xaxt) and ?axis for more information.

You can also use:

plot(x, y, axes = FALSE)

and then use axis(1, ...) and axis(2, ...) if you want to control both
the x and y axes, respectively.

HTH,

Marc Schwartz