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

[Daniel J S. <dan...@ie...>]

Ethan Merritt wrote:
> On Wednesday 16 August 2006 11:13 am, Daniel J Sebald wrote:
> 
>>Ethan Merritt wrote:
>>
>>>Someone on the usenet group reported a problem that boils down to
>>>  set log y
>>>  plot newhistogram "title",   <foo>, <baz>, ...
>>>
>>>The result is an error return
>>>  histogram has y coord of 0; must be above 0 for log scale!
>>>
>>>Now in fact the histogram itself is fine.
>>
>>How is this fine?  If one of the histogram bins has a value of 0,
>>log(0) is undefined.  Do you mean there is special code to deal with
>>this case?
> 
> 
> The error message comes from the title.
> Remove the title, no error message - the histogram itself has
> no problem.
> 
> The error message is totally a false alarm, based on checking
> the "offset" value of the title string.

Oh, yes now I see what you mean.  Well, the test should be against the eventual placement, not the offset, right?  Writing a patch for this would take a bit, but I don't see how one can do arithmetic on offsets using a logarithm scale, i.e., log(x+y) != log(x) + log(y).  I would guess this:

	    x = map_x((hist->start + hist->end) / 2.);
	    y = xlabel_y;
	    x += (int)xoffset_d;
	    y += (int)yoffset_d + 0.25 * term->v_char;

has to come before this:

	    map_position_r(&(histogram_opts.title.offset), &xoffset_d, &yoffset_d,
			   "histogram");

in some fashion.

Dan