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Manipulating VOTables with TOPCAT and STILTS. Tom McGlynn. What are TOPCAT and STILTS?. STILTS is a powerful library that enables users to filter and convert tables in VOTable and other popular formats.
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Manipulating VOTables with TOPCAT and STILTS Tom McGlynn
What are TOPCAT and STILTS? • STILTS is a powerful library that enables users to filter and convert tables in VOTable and other popular formats. • TOPCAT is a user interface built on top of STILTS with extensive GUI and graphics capabilities. • All written by Mark Taylor (Bristol University/UK) originally as part of the Starlink project. • This demo uses TOPCAT but the underlying functionality is available through the STILTS library (in Java). • There are some other standalone commands built on STILTS (e.g., votcopy). • There is a TOPCAT chapter in the NVO book.
Starting TOPCAT • In the standard distribution as command ‘topcat’ • Note capabilities to download data from various VO and other data sources. • Remember to run setup first! • Files used in this presentation: Download these (Twiki doesn’t let TOPCAT read them directly) • http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/spocs.csv • http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/spocs.xml • http://nvo-twiki.stsci.edu/twiki/pub/Main/NVOSS2008Sched/exostars.xml This URL can be used directly • http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=messier
Getting to and from VOTables • Converting to VOTables from CSV Load spocs.csv (available on Twiki) Save as spocs.xml (VOTable) Can covert into many formats. • Converting VOTables to CSV Load http://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=messier Save as CSV Portal tools may work better in handling data in non-standard formats.
Filtering data using TOPCAT • Show SPOCS table (view/tabledata) • Create a subset (view/row subsets/+) • Enter name=Sunlike • Enter criterion Teff>5720 && Teff<5820 && log_g>4.34 && log_g<4.54 && M_H>-0.1 && M_H <0.1 • Should create subset with ~30 rows. • Show with Views/Table data/Apply Subset/Sunlike • We can use column names or $number. • A sample can be saved in any of the supported formats.
Histograms • Click on histogram • Note which subsets are showing and click on all • Change column to VMAG • Note both all and sunlike data.
Plots • X/Y display • Ensure that full sample is shown. • Change parameters to Teff/Age • Zoom around sun location • Create new sample from plot (third box from right) • Note region selection tool (fourth from right)
3-D Graphics/Synthetic columns • 3-d displays (change third axis to something interesting in box) • Creating new columns: column metadata/+ • Name = AppMag • Expr = Vmag – 5*log10(Dist/10) [note striping error] • Note function browser • New columns can be used anywhere and show up on output
Correlations using TOPCAT • Load • SPOCS table • EXOStars table • Click on double match • Cross-correlate by position: • Find all the SPOCS stars that have exoplanets
Many more capabilities Direct access to VO enabled services Density plots Column data conversions Hundreds of functions usable in creating columns PLASTIC/SAMP communication with other tasks Joining tables Stacked plots or spherical plots Table statistics …