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Yorick to VOTable data translation


by Pichon Christophe (Saturday 6 October 2007)

Yorick to VOTable data translation

Jean Pichon 2007

A tool to generate VOTables from yorick structures used in Horizon.

JPG - 1.3 Mb
Example of VOtable visualisation
Examples in TOPCAT.

JPG - 688.7 kb
Aladin & MareNostrum
using VOtables

Purpose

The reduction of simulations in Horizon is often carried within yorick or Idl. In order to distribute the final tables within the Theoretical Virtual Observatory, we have produced a code which converts automatically any yorick structure into a VO table.

Method

Having defined the structures [1]


struct Leaf {
 int level;
 int mother;
}

struct Gal {
 int pos(3);
 Leaf leaf;
}

then, with


>g = Gal();

>d=VOExtractDescription(g);

returns


"pos = {datatype = <float>, arraysize = <*>}, leaf = (level = {datatype = <int>}, mother = {datatype = <int>})"

which can be used as an input [2] for "toVOTable":


>toVOTable, ["name = <particles>, datatype = <int>, value = <3>"], d, [g];

which yields

For more information, read "votable.i" (esp. with "help, toVOTable" and "help, VOExtractDescription") and the VOTable standard

Horizon Example

A more evolved example involves converting the first few objects of a structure such as those found in the spectral data structure:

For instance


~pichon/bin/upload  output_00040-specGal.pdb

then the structure, gals contains for its first element


> gals(1)  
Gal(leaf=CHalo(level=1,mother=1,firstchild=36693,nsisters=30595,sister=19819,
rho_saddle=81,density=10436,densmax=419636,radius=0.0191201,mass=1.65926e+06,
position=[0.913867,0.723709,0.408795]),pos=[0.913823,0.721701,0.405586],vel=
[-39.9842,-131.369,229.82],mass=3.83566e+10,redshift=4.55822,z_l=-2.75029,z_m=
-2.87464,age_l=93.4809,age_m=279.733,mag_obs=[70.7041,28.188,26.2333,26.3165,
26.3688,26.1744,26.0942,26.76,0,0,0,0,0,0,0,0,0,0,0,0],mag_abs=[-23.6841,
-23.9222,-23.9083,-23.6445,-23.7799,-22.8799,-22.139,-21.2689,0,0,0,0,0,0,0,0,
0,0,0,0],idx=0x84d6c0,spec=0x863960)

Following the same steps as before yields:

See this document

XML - 575.9 kb
Example of VOtable Horizon Table

for a larger sample of the structure in VOTable format.

Once the xml code has been generated, the fun is endless as illustrated on this example using TOPCAT. Here we scatter plot the first two fields:

JPG - 113 kb
Example of VOtable visualisation
Data generated from the spectral data extracted from a MareNostrum snapshot

WARNING: The data must be "VOTable-able", i.e. have a structure obviously mappable to the VOTable format as described here. This function implements VOTable version 1.1.

Possible extensions

- make the pointers open another page with possibly topcat or aladin ?

Special thanks to J. Pichon F. Bonnarel and M. Louys.

[1] Note that this is already a nested example.

[2] or modified by hand if required