On Thu, 26 Mar 2009, David Nutter wrote:
> I am trying to use wcstran to find the index of a 3D data cube that
> corresponds to a particular velocity/frequency. I can do this in
> reverse, and convert the array index (in this case 2185) to a velocity
> (VRAD) using:
>
> wcstran a20080301_00042_01_0001 framein=axis posin=\"2185,5,5\"
> frameout=DSBSPECTRUM-SPACEINDEX-TIME
>
> a1 = 2185.0 a2 = 5.0 a3 = 5.0 --> VRAD = -0.4973992 x2 = 5.5
> MJD = 2008-03-01 07:41:24
>
> However, I cannot get the grammar quite right for the other way. e.g.
>
> wcstran a20080301_00042_01_0001 framein=DSBSPECTRUM-SPACEINDEX-TIME
> frameout=pixel posin=\"-0.4973992,5.5,2008-03-01 07:41:24\"
>
> !! Extra characters ' 07:41:24' found at end of date/time value supplied for
> ! parameter POSIN - '-0.4973992 5.5 2008-03-01 07:41:24'.
> Please supply a new DSBSPECTRUM-SPACEINDEX-TIME Domain position for
> parameter POSIN.
> POSIN - Position to be transformed /'-0.4973992,5.5,2008-03-01 07:41:24'/ >
>
> The error seems to revolve around the format of the TIME coord (which
> is especially annoying, because I don't care what the time was, it
> makes no difference)
>
> If anyone could tell me how to resolve this, or suggest an alternative
> way of getting the index of a given velocity/frequency, I would be V.
> grateful for the info.
Hi Dave,
you'll have more success if you use a decimal number for the years, but
for a timeseries cube I couldn't get that to work either (the error
message claimed the inverse transformation wasn't defined). Try:
% atools
% asttrann this=a20080301_00042_01_0001 forward=t \
posin='"-0.4973992,5.5,2008.25"'
(2008.25 is just a guesstimate) instead. That did work for me.
Peter.
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