Re: Adding some new transformations to gnuplot (arctan and power laws)

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

On Wednesday 10 June 2009, pl...@pi... wrote:
> Ethan Merritt wrote:
> > On Wednesday 03 June 2009 14:15:52 pl...@pi... wrote:
> >> Ethan Merritt wrote:
> > 
> >>>
> >>> I am arguing that it may be preferable to send terminal coordinates corresponding
> >>> to linear scale, plus some clue how they should be transformed by the viewer
> >>> upon request.  
> >>>
> >> I'm wondering about the rationality of this. "Toggling" log/transform 
> >> scaling is really a euphormism for a total replot it seems. You 
> >> fundementally change the x or y scale transformation and have to do a 
> >> full replot of the data, axes and all.
> 
> [snip] 
>
> Mouse coords are intrinsically low res and one way. As you already noted 
> yourself a one off inverse transformation is easy to do off the plot. 
> Making this repeatable when toggling on and off requires the original 
> data otherwise accumulated errors and over-sensitive parts of the 
> mapping will rapidly cause unacceptable error.

Yes, well, that was exactly what I was proposing: send the untransformed
coordinates, and do all the transforms on the fly from the original 
full-resolution coordinates.
 
> The most obvious log transform could quickly produce significant 
> distortions unless the original data was reused.

Exactly.  So I think we are in complete agreement.

As it may not be obvious, let me point out that the canvas terminal,
like the cairo terminals, works with much higher precision coordinates
than the actual pixel display. The nominal resolution of the scripted
plot commands is currently 10x that of the display, but that could be
further increased if desired. The only downside is that the output script
would increase in size by, say, one decimal character per coordinate.

	Ethan