Re: Axis rescaling: [was: Re: Quick refresh [was: q for quit in plot windows]]

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

Ethan Merritt wrote:
> On Thursday 28 June 2007 14:32, Daniel J Sebald wrote:
> 
>>Ethan Merritt wrote:
>>
>>>My request was simply that you leave the existing
>>>log scale code in place until a general mechanism was ready to replace it.
>>
>>What do you mean by general?  Able to apply mappings other than log scale?
> 
> 
> Exactly.  I gave a bunch of examples earlier.
> The most common request (and hardest to work around) is marking off the
> X-axis as 1/x.   For instance, we crystallographers have to deal with 
> inconsistent usage all the time;  some quantities are given in terms of
> energy while others are given in terms of wavelength.  There is an
> inverse relationship:
> 	Energy = k / Wavelength
> where k is an appropriate constant.  It is a pain to try to persuade
> gnuplot to mark off both Energy and Wavelength on axes of the same plot.
> 
> I would like to be able to do something like:
> 
> 	set axis x1  x                 # will use for Energy
> 	set axis x2  k/x               # will use for Wavelength
> 	set axis y1  log(y)            # log scale value to be plotted
> 
> Even better if there is a way to automatically lock x1 to x2, so that
> they are forced to span the same range.

Sounds good.  I don't think anything I've done would effect the ability to provide such options.  Basically, LOG/DE_LOG could be MAP/UNMAP or some variation with functions.  There should be pairs of functions, one being the inverse function of the other.  For the sampled functions, instead of axis_unlog_interval(x_axis, &t_min, &t_max, 1) probably axis_linearize_interval() because that is what we are trying to do, i.e., some parameterization that for which linear spacing results in linear spacing on the scale whatever it is.

Not too difficult, I think, but I'd say get data storage squared away first.

Dan