[R] [OT] 'gv' and fractional points

[(Ted Harding)]

Hi Folks,

This is off-topic R-wise, but it may be close to
the heart of many R-users, so I think it may be
the best place to ask!

Users of 'gv' (the "front end" to ghostscript) will
be aware of the little window which gives you the
x-y coordinates (in points = 1/72 inch) of the position
of the "cross-hair" mouse cursor. These coordinates
are those of the corresponding position on the printed
page, relative to some origin.

I have often used this to extract numerical values
for data from graphs in Postscript files (also PDF
files, after you have converted them to PS). Then
(veering back on topic ... ) you can submit the
numerical data to R and try your own analyses on
these data, and compare with what the article does.

However, this little window only gives the numbers
in whole points. Say a smallish graphic may print
out 3 inches wide or high. Then you get precision
of 1/216 per 3 inches or 0.4% of full scale. This
can be adequate on many occasions, but can be on
the coarse side on other occasions.

Even for a 6-inch-wide/high graph, you only get down
to 0.2% of full scale.

If it were possible to induce 'gv' to display these
coordinates in tenths of a point, then much greater
precision (as adequate as one can expect to hope for
when, in effect, "measuring off the graph") could be
obtained.

Does anyone know:
a) Whether it is possible to persuade 'gv' to give
   this display in fractional points (my own search
   of the documentation has not revealed anything);
b) Of any alternative to 'gv' as PS viewer which would
   provide this capability?

With thanks, and best wishes to all,
Ted.

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E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 15-Jun-07                                       Time: 16:13:21
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