Re: [ 1004754 ] Tics and grid slightly outside border.

[Ethan M. <merritt@u.washington.edu>]

On Wednesday 28 June 2006 08:07 am, Petr Mikulik wrote:
> > I've placed a patch under bug report [ 1004754 ] on SourceForge
> > that is a cleanup of the tic generation.  I think it would be worth
> > considering for 4.2, because it does fix the bug and it is much
> > friendlier computer math
>
> I propose to commit it.
>
> Notes: "logorithm" => "logarithm"

I have not analyzed the code itself, and don't have time to 
do so right now.  But the cover explanation contains an 
off-by-one error in the algorithm, so I worry that it is not
correct.

> number of intervals, N_int
>    /* Address rounding issues in the following way */
>    if (i_tic == (N_int - 1))
>	tic = end;
>    else
>	tic = start + i_tic * step;

This is an off-by-one error, an instance of the "fencepost problem".
The obvious case is when there is one interval, so (N_int-1) == 0 ,
and the above code puts both tics at the same end of the axis.












>
> (I wish also the "rounding" plot [-1:1] patch...)
>
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle WA