On Mon, 19 Jan 2004, Nick Cox wrote:
> That said, users re-creating graphs for [time series]
> data from first -graph- principles are likely to be bit
> by a problem of spurious connections joining together
> curves from two or more individuals whenever
> the last data point for one person is no
> later than the first data point for the next person.
> This may be rare, but it does occur. The graphical problem
> is soluble, but fiddly.
That's an interesting contrived objection, and raises the point that
authors of graphics be sensitive to problems and should proofread graphs
just as carefully (or more so!) as someone writing text should check for
typos, malapropisms and other unintended errors of communication.
The distinction c(l) versus c(L) that enables Stata graphs to draw
multiple lines within one variable has always struck me as a nice, elegant
feature that gives power when articulating the drafting process. The
suggested problem will not arise in a conventional repeated-measurements
experiment but will occur in a longitudinal study where panel members drop
out and are replaced. Having just tried xtline, one difference between
the two suggested methods is that xtline does not allow point labelling
on the lines, but appears to demand a legend. That does not seem feasible
with 604 lines.
R. Allan Reese Email: [email protected]
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