[Kst] Re: CDF datasource debugging ?

Barth Netterfield netterfield at astro.utoronto.ca
Thu Jul 15 19:59:47 CEST 2004

On July 15, 2004 11:57 am, Nicolas.Brisset at eurocopter.com wrote:
> > and the samples are assumed to be
> > evenly distributed through the frame.
> That's just the problem I have. In the data I'm using (you may look at a
> typical example in the .cdf file I sent recently), there are "blocks" which
> you can imagine as groups of columns. In each group, the first column gives
> the cycle number of the recording computer in which the variables in the
> following columns were measured, but it is NOT evenly spaced. It is not a
> "hard" real-time environment, and records may come one cycle earlier or
> later :-(
> That makes it very difficult to implement the scheme you describe, and I'd
> much prefer to return the biggest number of records for the whole file in
> frameCount(), 1 in samplesPerFrame(...), and handle the fact that some
> variables have less points in readField() by returning 0 (or -1) when asked
> for values beyond the last available for this field, treating it as a sort
> of error. It means that X=INDEX will not be consistent in my case, but if I
> use the right cycle for X then things will be OK. Do you foresee any
> problem with this approach ?

Two options:
	1) Encode 'group/block' awareness into kst.  So a data-source presents 
	a group.   Perhaps a syntax like "/data/datafile.cdf:group1" for the
	 file name?
		+ everything within a block (group) appears to be consistent with 
		how kst thinks. (sampled together, with an x-axis variable availible)
		- May require changes to the kst UI. (eg, dataselector needs to know about 
groups for, eg, auto completion)
	2) do as you suggest, but use NAN rather than 0 or -1.  kst gracefully deals 
with NANs as much as is possible.
		+ pretty easy
		- not a nice solution for looking at the data.

I really don't like #2.  If we can do #1, it will be a lot better I think.
George, how did you end up dealing with implementing #1 in piolib?


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