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

From: Ted Harding <>
Date: Fri, 15 Jun 2007 20:33:34 +0100 (BST)

On 15-Jun-07 15:56:58, hadley wickham wrote:
> 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:
> Hadley

Thanks, Hadley! But (as you implicitly surmise) I don't use a Mac (just non-psychedelic Linux).

However, as a follow-up, I've since found that one can (somewhat tediously) do what I was asking with the GIMP.

If you start the GIMP on a PostScript file, you initially get a "Load PostScript" window which asks you to choose (amongst other things" the "resolution", initially "100". If you wind this up to say "1000", then you get 10 times the positional precision in the numbers shown as below.

When the image is displayed, there is again a little window which gives you the GIMP coordinates of the mouse position. With increased "Resolution", the numerical values vary correspondingly more rapidly with position.

The tedious aspect (compared with 'gv') is that to get better visual resolution you need to zoom the image. This enlarges the whole image, with the result that you have to pan around to locate different parts, and you can get lost in a graph with lots of widely-spread points.

With 'gv', on the other hand, you can select any small part to view in zoom in a sub-window, which is much easier to cope with; and you also get a "rubber-band" rectangle which enables you to readily align points here with points there -- e.g. if you want to read off a curve the y-value corresponding to say x=5.0.

However, this is at least a partial answer to my own question!


E-Mail: (Ted Harding) <> Fax-to-email: +44 (0)870 094 0861
Date: 15-Jun-07                                       Time: 17:29:49
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E-Mail: (Ted Harding) <> Fax-to-email: +44 (0)870 094 0861
Date: 15-Jun-07                                       Time: 20:32:59
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