Re: [Gnuplot-info] ugly data-point rounding error

[Thomas S. <t.s...@fz...>]

don't know with which version of gnuplot these plots were
generated, but since version 4.0 SVG_SCALE is 10.
i'm not able to reproduce this poor quality with
gnuplot 4.0, 4.2.5 and 4.3-cvs.


Ryan Davis-4 wrote:
> 
> Hi,
> 
> I realized some strange jiggling of plotlines in many
> svg-gnuplot-graphics. Especially when a plot is supposed to be precise
> and many datapoints are used, the problem gets worse.
> 
> Seeking
> for the bug in the sourcecode, it turned out the problem is that every
> datapoint to be drawn is handed over as an integer, e.g.
> 
> TERM_PUBLIC void SVG_vector (unsigned int x, unsigned int y) .
> 
> In
> case of the standard-settings SVG_SCALE=1 , this means, that every
> point is binned to integer-pixelvalues, rendering the whole sense of
> vector-graphics useless.
> 
> Some examples where the problem is directly visible:
> http://commons.wikimedia.org/wiki/File:Normal_distribution_cdf.svg
> http://commons.wikimedia.org/wiki/File:Soliton_2nd_order.svg (see the grid
> on the ground which is supposed to be
>  flat)
> http://commons.wikimedia.org/wiki/File:Arcsin_plot.svg
> 
> if you don't see what I mean, take a look at the 2000px versions. Many
> graphics of this kind can be found on the internet.
> 
> 
> Since
> it's not a problem concerning only svg-export but a flaw rooting deep
> inside gnuplot, i cant't correct it by myself. Gnuplot is used in many
> scientific applications and I'm absolutely convinced, that treating
> data-points as float values is the only reasonable choice. Those
> terminals who only support raster-images can round the values later on,
> and even they can take advantage of precisely located data-samples. As
> a user, I don't know how to solve it, so I hope you can fix this in the
> sourcecode. Floating-point output to svg-files with at least 3 digits
> precision seems essential.
> 
> thanks in advance!
> 
> 
> 
> btw: did you notice inkscape's inability to interpret the
> "color"-attributes in gnuplot-created svg-graphics? maybe it helps to
>  assign stroke- and fill-colors directly.
> 
> 
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