[R] stripchart problem

[Alexandre Irrthum]

Hello,

I am trying to plot age distribution data for a certain condition that
runs in families. Below is a simplified view of the dataset, i.e. in
this case there are four families, each line corresponding to one
individual with age at diagnosis and sex.

> famdata
   family age sex
1    fam1 2.1   f
2    fam1 2.3   f
3    fam1 1.0   m
4    fam2 7.3   f
5    fam2 4.1   f
6    fam2 1.2   f
7    fam2 0.6   m
8    fam3 3.5   m
9    fam3 2.5   m
10   fam3 2.9   m
11   fam3 5.6   m
12   fam3 4.4   f
13  fam10 1.1   f
14  fam10 1.2   f
15  fam10 2.9   f
16  fam10 2.2   f
17  fam10 4.7   m

I can nicely plot the age distribution by families with

> stripchart(famdata$age~famdata$family)

I would like to plot datapoints according to the sex of the person, e.g.
circle for a girl and square for a boy, like this:

> stripchart(famdata$age~famdata$family, pch=ifelse(famdata$sex=="m",
22, 1))

But this command doesn't work as I expected. Datapoints from fam2 are
shown as squares, all the rest as circles. Still , this seems OK:

> ifelse(famdata$sex=="m", 22, 1)
 [1]  1  1 22  1  1  1 22 22 22 22 22  1  1  1  1  1 22

Any clues ?

Thanks a lot for your help,

alex