Simple use case for SAMP ??

[Mark Taylor]

On Wed, 18 Feb 2015, Petr Skoda wrote:

> The same with TOPCAT
> 
> Loading the MAGIC example in it -  it does not allow to interpret tupples so
> it gives me no chance to select and plot coordinates in its plotting window  -

You can do it, but it doesn't make it very obvious for you.

The expression language lets you refer to tuple (array) elements
individually using square brackets, so typing in the coordinates
for a plot as

   Lon:  SpatialLocation[0]
   Lat:  SpatialLocation[1]

or even

   Lon: utype$ssa_Char_SpatialAxis_Coverage_Location_Value[0]
   Lat: utype$ssa_Char_SpatialAxis_Coverage_Location_Value[1]

will give you a sky plot.

Alternatively, if you select the SpatialLocation column in the
Columns window
(http://www.star.bristol.ac.uk/~mbt/topcat/sun253/ColumnInfoWindow.html)
and hit the "Columns|Explode Array Column" menu item or equivalent toolbar
button, it will replace that tuple column by two scalar ones which
you can then use as normal.

The same comments apply to using these values for things other than
plotting.

> I still feel it should as the coordinate tupple is official VO "datatype"

Yes, it probably should (though these array columns are a bit of a pain).
I'll try to see if I can do something about it when I get the chance.

Mark

--
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-9288776  http://www.star.bris.ac.uk/~mbt/