Re: [bug] plot bins does not clip output to plot area

Ethan A Merritt writes:
>> I'm using it as a way to average over a large number of samples that are
>> sampled equidistantly (kernel density is way slower obviously). The
>> documentation doesn't really tell how it is implemented or supposed to
>> work, so I've experimented a bit to find out.
>
> I take the blame for any failures in either the implementation or
> the documentation of the "bins" option, since I wrote both.
> I would be happy to amend the code or the description to cover
> uses that I didn't anticipate.

No blame to go around… any feature is prone to be (mis)used in ways
never intended, once it's there.  :-)

> Since I envisioned it as a histogramming tool, it did not occur to
> me that users would want to plot "with lines" rather than using
> boxes or impulses.   Therefore I did not think about or test the
> clipping behaviour.

No good deed goes unpunished, as they say.

> As it happens, the routines that draw boxes or impulses do the clipping as
> they draw each one.  The routine that draws "with lines" assumes that the
> inrange/outrange/undefined status of each point has already been flagged,
> and only considers clipping if a particular line segment changes state.
> This is so that successive in range points are drawn as a single poly-line
> with smooth joins rather than being split into individual segments.
> Normally the inrange/outrange flag is set on data entry, but those flags
> apply to the original data points rather than to the binned totals.
> I have now added a separate pass to re-check the binned data against
> yrange so that clipping works as you expect it to.
> (New code added for both 5.4 and 5.5).

Great, I'll check it out later.

> I remain a little uneasy about the use of negative values in the weighting
> column, although I don't have a specific example in mind that will fail.

So far I have not yet encountered any problems with that and I have
likely given this part quite a bit of exercise as most of the data I'm
plotting is roughly centered about zero.

> Thanks for the explanation of what you are using it for.
> I agree that in that mode "bins" is similar to a kernel density model
> that uses a delta function rather than a Gaussian kernel.

I would suggest that it would be welcome if one could specify the kernel
function and/or provide a way to implement general FIR filtering on the
original data.  While the moving average trick is cute, it is also quite
slow and cumbersome once you need to average over a large number of
samples.

> I may not have phrased that well.  It weights the _contribution_ of each
> sample by the value in the seconds column.  If no second column is
> provided, the weight is 1.

That seems a more accessible description to me, thanks.


Regards,
Achim.
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