Sun 31 Jan 2016 08:13:53 AM UTC, comment #6:
Michael, I agree that documenting the limitation is useful as a backup.
Panxto, I agree that we need to choose a rule for both major and minor tics in a consistent way.
One problem with basing the spacing on the number of pixels is that things like PDF don't really have pixels. It may be useful to use the width and height of a character of the label font as a unit.
I would use a rule of thumb that the space between consecutive labels should be no less than approximately the width of a label (which depends on the number of digits in the label as well as the font size).
Given the major tics, we could have as close as possible to 4 minor tics per major tic, while staying with one of the sets:
10^0, 10^n, 10^2n, ...
1,3,10,30....
1,2,5,10,20,50...
1,2,3,5,7,10,20...
1,2,3,4,5,6,7,8,9,10,20,...
(or something finer if the major tics are very close)
Some packages refuse to have major tics closer together than a power of 10, but that often leads to plots that quite hard to read.
Again, $0.02
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Wed 07 Oct 2015 11:43:26 AM UTC, comment #5:
It is pretty widely accepted that a completely
general solution for automatic tick marks does not
exist. But, trying to avoid the recent problems is,
of course, worth doing. Imagining that these fixes
will "always" work is not appropriate.
It may be helpful to put something in the Manual to
point out that manual control of tick marks may be
needed, or at least useful to improve the result,
in special cases.
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Wed 07 Oct 2015 11:27:22 AM UTC, comment #4:
@Avinoam: then you end up with bug #39449, which is minor ticks are no more computed correctly.
I think fixing bug #39449 involves being able to compute minor ticks when major ones are not distant of one order of magnitude. For this we should first decide what to do when minor ticks come to be be ridiculously close to each other:
- use a fixed tule: show 2:9 if tick_sep < 6, then 2:2:9 for ticksep <10, then 2:3:9 ...
- use a rule based on the minor tick separation: e.g. minimum 2 pixels between two minor ticks.
There may be other rules we can imagine but it is only once one of those rules has been chosen that we can fix both this bug and bug #39449. This is my 2cts.
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