Cube/ImageDM - new diagram set.

[CresitelloDittmar, Mark]

Arnold,

A couple points to think about.
  - if I read this properly, you are saying that tabulated data may be
modeled as a
    pixel axis (row#) with lookup transforms to the various 'physical' axes
(columns).
    * I agree, one could do that, but am not sure that I would call it
preferable.
  - I see an issue with virtual columns (WCS defined)
    + in a chandra event list, the eqpos(ra,dec) columns are defined as a
WCS projection
       of the 'actual' columns sky(x,y).
    + since the LOOKUP to sky is non-linear, one cannot define a LOOKUP
from the
       pixel axes to the eqpos(ra,dec) columns.  ie: one cannot define a
'LINEAR' stage
       as one can in the image case.

My thinking as you describe:
  - the SparseCubeDataset (currently HyperCubeDataset) is a collection of
points
    occupying ND data space, and forms the head of the dataset types which
can be
    represented in tabular form.
  - by binning/collapsing axes, and explicitly creating pixel axes, one
generates
    NDImageDataset (currently ImageDataset), and forms the head for 'image'
forms.
  ** I suppose this is more the "ImageData" node level. **


Mark




On Sun, Apr 6, 2014 at 6:13 PM, Arnold Rots <arots at cfa.harvard.edu> wrote:

> I want to say something about enumerated axes. It relates to one aspect of
> Mark's model
> in particular and the connection will become clear.
>
>
>
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