[R] plot (cox)

[Medic]

In this code:

plot (cox, col=1:2, xscale=1, xlab="OS",  ylab="Probability")

the X scale is divided (by default) as:

 0 ... 50 ... 100 ... 150 ... 200

And I would like so:

0 ... 12 ... 24 ... 36 ... 48.

I looked ?plot(cox), but did not understand what argument is
responsible for this.

Pls, help me!