Hi Simon- > Full Name: Simon Metcalf > Email Address: address@hidden > Organization: NSW Rural Fire Service > Package Version: 2.7u2 build date:2009-08-26 16:33 UTC > Operating System: Windows XP > Hardware: Java: home: C:\Program Files\IDV_2.7u2\jre version: 1.6.0_13 > j3d:1.5.2 fcs (build4) > Description of problem: Dear Team, > > Does anyone have a working function for U & V to Wind Direction? I've tried > to build the function myself but have run into problems, particularly its > inability to recognise pi and also how to build IF statements into a 1-line > function. The closest I got was as follows, which (if pi worked) would > return values between -180 and 180 degrees. Is it possible to add this > function to the default (derived functions) in future versions so the > multi-coloured Flow Vectors from WSpd and WDir work using U and V? > > atan2(-1*U,-1*V)*180/pi Use either the dirn()(north direction) or dirr()(grid relative) function. If you have a lat/lon grid, just use dirr(vecr(u,v)). Otherwise, use dirn(vecr(u,v)). See the griddiag section of this page: http://www.unidata.ucar.edu/software/IDV/docs/userguide/tools/JythonLib.html Don Murray Ticket Details =================== Ticket ID: XIW-870909 Department: Support IDV Priority: Normal Status: Open
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