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

From: hadley wickham <>
Date: Fri, 15 Jun 2007 17:56:58 +0200

This doesn't answer your original question, and isn't much help unless you're on a mac, but there's a nice looking program that makes this kind of graph scraping really easy:


On 6/15/07, Ted Harding <> wrote:
> 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.
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <>
> Fax-to-email: +44 (0)870 094 0861
> Date: 15-Jun-07 Time: 16:13:21
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> mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Fri 15 Jun 2007 - 16:00:56 GMT

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