# [R] xaxp and yaxp

Uwe Ligges ligges at statistik.uni-dortmund.de
Sun Mar 10 18:45:53 CET 2002

```Arne Mueller wrote:
>
> Hello,
>
> I'm new to R, and I'm trying to set the number of tickmarks for a plot
> using xaxp, but R seems to ignore this setting completely. Maybe you've
> an idea what I'm doing wrong. I'm using R 1.4.1, and here's hat I'm
> doing:
>
> > d[,'seq']
>  [1] 28913 16323 13922  6237  4257  3881  4100  3781  2694  2064  1769
> 1550
> [13]  1539   480
>
> > d[,'scop.dup.rate']
>  [1] 97.7 95.3 95.3 88.5 84.6 84.6 84.7 82.8 71.5 74.9 74.9 71.2 67.8
> 54.9
>
> > plot(d[,'seq'], d[,'scop.dup.rate'], col="red", pch=22, bg='red', cex=1.5, xlim = c(0,30000), ylim=c(20,100))
>
> tick marks are placed at 0,5000, ... 30000 for the xaxis.
>
> now I'd like to have more tickmarks
>
> > plot(d[,'seq'], d[,'scop.dup.rate'], col="red", pch=22, bg='red', cex=1.5, xlim = c(0,30000), ylim=c(20,100), xaxp=c(0,30000,13))
>
> tickmarks are set the same way as above.
>
> Also par(xaxp=c(0,30000,13)) does not change anything ... :-(
>
> I'd like to have 13 tick marks on the x-axis including the extreme ones
> (0 and 30000).
>
> I'm not sure whether I realy understand what xaxp is doing, so I thought
> it may need the interval:
>
> par(xaxp=c(0,30000,2500))
>
> hm, but this doesn't change anything either :-(

In your case you should set the tickmarks manually using axis(), e.g.:

plot(..., xaxt="n")
axis(1, at=seq(0, 30000, length=13)

If you don't specify the loactions manually the function pretty() will
be used in principle.

Uwe Ligges
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```