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Re: Get Graphics Coordinates accuracy

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92348] Re: Get Graphics Coordinates accuracy
  • From: m.r at inbox.ru
  • Date: Sun, 28 Sep 2008 07:21:54 -0400 (EDT)
  • References: <gbjm5i$383$1@smc.vnet.net>

John Jowett wrote:
> I came across a limitation in the mechanism for copying coordinates of
> points in 2D graphics (the Get Coordinates button in the Drawing Tools
> palette) in V6.03.
>
> Consider the following plot of a sine wave
>
> Plot[Sin[2 x], {x, 20270, 20275}]
>
> When I try to select and paste the coordinates of the two crests of
> the wave, I typically get two points with the same x-coordinate
>
> {{2.027*^4, 0.99}, {2.027*^4, 0.99}}
>
> whereas I would expect the two x-coordinates to be around
> 20270.3 and 20273.5, values which are well separated on the plot.
>
> This seems to happen because the Get Coordinates function only returns
> the first 4 digits of the coordinates.
>
> Does anyone know of a way to fix this ?  Obviously, in this
> demonstration example, I could change variables to x1=x-20270 but in
> the more complicated problem I am working on, this is not so easy.
>
> John Jowett

As a workaround, you can do

Plot[Sin[2 x], {x, 20270, 20275}, CoordinatesToolOptions ->
 {"DisplayFunction" -> (#&),
  "CopiedValueFunction" -> (SetPrecision[#, $MachinePrecision]&)}]

and then you can apply N to the copy-paste result to convert it back
to MachinePrecision.

Maxim Rytin
m.r at inbox.ru


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