On Tue, 29 May 2001, Peter Nash wrote:
> Do you know any statistical software shows on a scatter-plot when
> points are coincident (i.e. there are numerous points that overlap in
> one location)? This is sometimes shown using jitter, sometimes
> different sizes for the points, sometimes adding leaves to the points
> to indicate the number of overlapping points, and sometimes this can
> be performed by changing a 2D graph to 3D.
>
> This feature is crucial because it IMMEDIATELY shows the importance of the
> points. (Not Minitab, which insists on jittering ALL the plotted points)
You must be referring to Minitab's "Professional Graphics". Invoke the
old character graphs (the command is GSTD for standard graphics). The
PLOT command (or the equivalent menu request) produces scatterplots in
which a single observation is represented by an asterisk (*), multiple
observations are represented by the number of such observations if that
number can be represented in a single digit (2-9), and by a plus sign
(+) if 10 or more observations occur at that point. If the standard
output is too coarse for your taste, expand the scale via the HEIGHT and
WIDTH commands.
Of course, if your data set is so large that most of the plotted points
are multiple, and if many of them have more than 10 duplicates, this will
not help a whole lot...
By the bye, are you sure that Minitab "insists" on jittering? I'd
thought that was an option that could be turned on or off; perhaps it's
the default in your system, or your release of Minitab, but I'd expect
that one could turn it off. I don't have an installed copy handy on
which to test that conjecture, however.
-- DFB.
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Donald F. Burrill [EMAIL PROTECTED]
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