Presentation on theme: "Manipulating VOTables with TOPCAT and STILTS Tom McGlynn."— Presentation transcript:
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 doesnt 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.xmlhttp://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
Starting and loading a URL
Table loaded successfully
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 bin/W3Browse/getvotable.pl?name=messier bin/W3Browse/getvotable.pl?name=messier Save as CSV Portal tools may work better in handling data in non-standard formats.
Convert to a CSV file
After loading CSV convert to VOTable
The table browser
Filtering data using TOPCAT Show SPOCS table (view/tabledata) Create a subset (view/row subsets/+) –Enter name=Sunlike –Enter criterion Teff>5720 && Teff 4.34 && log_g -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.
Creating a subset
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)
Creating a subset graphically
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
Creating a new column
Correlations using TOPCAT Load –SPOCS table –EXOStars table Click on double match Cross-correlate by position: –Find all the SPOCS stars that have exoplanets
Viewing the correlation
Saving the correlated data.
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 …