matplotlib-devel Mailing List for matplotlib

On Thursday 04 March 2010 14:20:41 you wrote:
> 2010年3月4日 Günter Lichtenberg <Gue...@dl...>:
> > Hi
> > 
> > I think there is a bug in the conversion routines jul2num() and
> > num2jul(). I tried to define a date axis for satellite data. The time is
> > measured in a modified Julian Date (JD). So reading in the data and then
> > doing
> 
> Hi Günter,
> 
> Thanks for digging into this. Could you file a report on the bug tracker
> 
Done under
2963391 Wrong conversion in julian2num/num2julian
gl
-- 
Dr. Günter Lichtenberg
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
Institut für Methodik der Fernerkundung (MF-AP)
82234 Weßling
Tel. +49-8153-28-1331
Fax +49-8153-28-1446
Gue...@dl...

2010年3月4日 Günter Lichtenberg <Gue...@dl...>:
> Hi
>
> I think there is a bug in the conversion routines jul2num() and num2jul(). I
> tried to define a date axis for satellite data. The time is measured in a
> modified Julian Date (JD). So reading in the data and then doing
Hi Günter,
Thanks for digging into this. Could you file a report on the bug tracker
http://sourceforge.net/tracker/?group_id=80706&atid=560720
Thanks,
JDH

Hi 
I think there is a bug in the conversion routines jul2num() and num2jul(). I 
tried to define a date axis for satellite data. The time is measured in a 
modified Julian Date (JD). So reading in the data and then doing
mp = julian2num(jd)
dates = num2date(mp)
resulted in an error "year out of range" (or so). I looked at the values and 
they were way to high. Inspection of the source date.py showed for the 
conversion routines
julian2num: j + 1721425.5
num2julian: j - 1721425.5
Since the JD measures days from 4713 BC - earlier than the matplotlib 
zeropoint - the conversion should be the other way round, i.e. for julian2num 
we should subtract. 
After correcting this, I could still not reconcile my measurement dates with 
the result of num2date(). In the source it is stated that counting starts at 
0001年01月01日 00:00:00 UTC (JD 1721423.5), which BTW does not match the number 
used in the routines. The only way to correct this was to use an offset of JD 
1721424.5 (January 2nd, 0001, 00:00:00). 
So the correct formulae should be
julian2num: j - 1721424.5
num2julian: j + 1721424.5
or am I missing something?
VERSION INFO: matplotlib V. 0.99.1.1/python 2.6.2
on opensuse 11.2/x86_64
Cheers
gl
-- 
Günter Lichtenberg

Should be fixed with r8178.
Regards,
-JJ
On Wed, Mar 3, 2010 at 5:19 PM, Jae-Joon Lee <lee...@gm...> wrote:
> On Wed, Mar 3, 2010 at 4:48 PM, John Hunter <jd...@gm...> wrote:
>> JJ is this related to your commit in r8035 : "support
>> unsampled image for ps backend"
>
> It seems to be.
> I'll take a look.
>
> Regards,
>
> -JJ
>