missing warnings...

[Martin Maechler]

>>>>> "PD" == Peter Dalgaard BSA <p.dalgaard@biostat.ku.dk> writes:

      <....>

    PD> Boxplot expects a *factor* as the grouping criterion. The x axis
    PD> labels are the group names, not x coordinates (i.e. it might as well
    PD> be "married, unmarried, divorced" as "0, 1, 2."), and since factors
    PD> are internally coded as 1:nlevels, that's the value used for the
    PD> actual coordinate system.

    PD> Passing a numeric vector gets it converted to a factor before use, so
    PD> things are as you should expect. Except possibly for two issues:

    PD> a) should one really do the numeric->factor conversion without a
    PD> warning message?

Yes, we should have that warning (and more!):

Warning messages that I am extremely missing are in the following two examples

  plot(1);  points(2,2)

  plot(1);  text(2,2,"bla")

(and similar with lines and all kinds of plots).

We *definitely* should warn the user that (s)he is drawing outside the plot
region.  
We need "graphical warnings" 
   (which can be turned off via an options() or par() call).

    PD> b) perhaps boxplot could use an at= argument saying "plot boxes here"
    PD> since the current version wouldn't be able to deal with
    PD> non-equidistant groups. 
oh yes!
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