Re: Interesting bug: relative offset + log scale = problem

[<br...@ph...>]

Ethan Merritt wrote:

> I am leaning towards the idea that map_position_r() needs a
> top level check on entry for zero offsets.
> Who cares whether it's zero characters, zero plot units,
> or zero something else?
> Zero is zero.

Not on a logarithmic axis it ain't.  On a logarithmic axis, offset zero 
is actually negative infinity.  If the user wanted an offset of 
_visually_ zero, then on a log axis the gnuplot way of saying so would 
be to specify an offset factor of 1.

> But it may also be true that map_position_r() should never
> do range checking, even for non-zero offsets.  

Then you should be glad --- because it doesn't actually do range 
checking.  It does illegal value checking on logarithmically scaled 
values, which is a different thing.

This is ultimately a usage error we're looking at, possibly caused by 
insufficient documentation.  In gnuplot, the tradition is that 
increments to logarithmic values are specified as values that have to be 
logarithmized, following the way 'set xtics <incr>' behaves on log axes:

	set log x
	set log y 2.0
	set ytics 16
	plot [1e-3:1e3] x

The offsets of axis labels and titles should work the same way.