plot - R Draw All Axis Labels (Prevent Some From Being Skipped)

Question

When I manually add the following labels with (axis(1, at=1:27, labels=labs[0:27])):

> labs[0:27]
 [1] "0
9.3%"  "1
7.6%"  "2
5.6%"  "3
5.1%"  "4
5.7%"  "5
6.5%"  "6
7.3%"  "7
7.6%"  "8
7.5%"  "9
7%"    "10
6.2%" "11
5.2%"
[13] "12
4.2%" ........

I get the following:

How do I force all labels to be drawn so 1,3,5,6, and 11 are not skipped? (also, for extra credit, how do I shift the whole thing down a few pixels?)

Answer 1

If you want to force all labels to display, even when they are very close or overlapping, you can "trick" R into displaying them by adding odd and even axis labels with separate calls to the axis function, as follows:

labs <-c("0
9.3%","1
7.6%","2
5.6%","3
5.1%","4
5.7%","5
6.5%","6
7.3%",
         "7
7.6%","8
7.5%","9
7%", "10
6.2%","11
5.2%","12
4.2%",13:27)
n=length(labs)
plot(1:28, xaxt = "n")
axis(side=1, at=seq(1,n,2), labels=labs[seq(1,n,2)], cex.axis=0.6)
axis(side=1, at=seq(2,n,2), labels=labs[seq(2,n,2)], cex.axis=0.6)

You can play with cex.axis to get the text size that you want. Note, also, that you may have to adjust the number of values in at= and/or labels= so that they are equal.

I agree with @PLapointe and @joran that it's generally better not to tamper with R's default behavior regarding overlap. However, I've had a few cases where axis labels looked fine even when they weren't quite a full "m-width" apart, and I hit on the trick of alternating odd and even labels as a way to get the behavior I wanted.