RC5 proposal: Cleaning up "plot smooth"?

[Philipp K. J. <ja...@ie...>]

The "plot smooth" facility has grown over time;
currently it has eleven (11) suboptions, and I
can see this number to grow even more.

What's more, these suboptions do quite different
things. I can identify four major groups:

1) smooth interpolations:
  csplines, acsplines, mcsplines, bezier, sbezier

2) visualization of point distributions
  kdens, cumulative, cnormal

3) dedupe
  frequency, unique

4) unwrap 
  (which I have not yet figured out how to use)

The only reason that they all are presented to 
the user as "smooth" options is that they all
are implemented using similar facilities, but 
not because they are logically similar. (In 
particular items 1 and 2 do quite different 
things. And it's not even as if all of the 
suboptions add a "smooth curve" to the data - 
items 3 and 4 do not!).

Question: would it make sense to break this up
now, before it gets any bigger? And if yes: how?

Since introducing new keyword(s) would imply a
possibly non-backwards compatible change, now is
the time to think about it!

Here is one suggestion (total strawman - just to
get the discussion going):

item 1: plot smooth ... (interpolations)
item 2: plot distrib ... (point distributions)
item 3: plot dedupe ... (?)
item 4: plot unwrap ...

Full plot commands would then look like:

plot "data" u 1:2 smooth csplines 
plot "data" u 1:2 distrib kdens
plot "data" u 1:2 dedupe unique

and so on.

Question: is this a good idea? And: is this worth it?

More importantly: is there some refactoring that
could/should occur at the same time on the 
implementation side? 

One thing I foresee is that people will continue
to add additional algorithms (3 have been added 
since I last looked) - for instance, I am toying
with an algorithm to do LOWESS interpolation, and
I can also see the desire to add new smoothing
kernels to kdens. And on and on.

Would it make sense to pull things apart now, both
from the user-interface point of view, and on the
implementation side?

Best,

		Ph.