# [R] 2 plots sharing axis / combining factors

Petr Pikal petr.pikal at precheza.cz
Tue Oct 1 13:42:48 CEST 2002

```Hi

On 30 Sep 2002 at 17:22, juli g. pausas wrote:

> Dear R users,
>
> - Is it possible to produce a figure with 2 plots that they share one
> of the axis, e.g., the y-axis? I did not succeed by setting mai[4] <-
> 0. Is there a simple way?
>
> - How could I convert 2 factor variables in a single factor variable
> which is the combination of the other 2. Example:
>     lith: a factor 2 levels "ca", "ma"
>     sp: a factor with 2 levels, "ph", "qi"

interaction(f1,f2)

works if f1 and f2 are factors with the same length

if one factor is shorter than the other the shorter one is recycled

> and I'd like to obtain:
>     splith: a factor with 4 levels: phma, phca, qima, qica
>
> on way is by using ifelse:
>
> splith <- as.factor(ifelse(sp=="ph", ifelse(lith=="ma", "phma",
> "phca"), ifelse(lith=="ma", "qima", "qica")))
>
> which works fine, but I've got the feeling that it can be done in a
> more efficient way, especially for other cases where factors have more
> than 2 levels.
>
>
> Thanks in advance for any suggestion
>
> Juli
>
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Petr Pikal
petr.pikal at precheza.cz
p.pik at volny.cz

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