Re: First function debug help

• To: mathgroup at smc.vnet.net
• Subject: [mg106665] Re: [mg106627] First function debug help
• From: Herman Kuun <oomkoos1 at gmail.com>
• Date: Wed, 20 Jan 2010 06:50:48 -0500 (EST)
• References: <201001191013.FAA29027@smc.vnet.net>

```The hour input 'h_' is not used in the defined function.

Substitute
d = d + ((m * 60 )/ ( 24 * 60 )) + ((s * 3600)/(24 * 3600));
with
f = d + (h/24) + (m/(24*60)) + (s/(24*3600));

Also try make it a habit to start your own variable and function definitions
in lower case. Mathematica uses upper case exclusively. Save you lots of
frustration in the future.

This will calculate corectly:
------------------------------------------------------------------------------------------------------------

julianDayModified[y_, m_, d_, h_, m_,   s_] := (

b = 2 - IntegerPart[y/100] + IntegerPart[IntegerPart[y/100]/4];

f = d + (h/24) + (m/(24*60)) + (s/(24*3600));

jd = IntegerPart[(365.25*(y + 4716))] +
IntegerPart[(30.6001*(m + 1))] + d + b - 1524.5;

mjd = jd - 2400000.5;

mjd

)

julianDayModified[2010, 1, 1, 12, 0, 0]

55164.

---------------------------------------------------------------------------------------------------------------
Best
Herman

On Tue, Jan 19, 2010 at 12:13 PM, Canopus56 <canopus56 at yahoo.com> wrote:

> I took a stab at writing my first function - converting a system formatted
> list date into a Modified Julian Day.  The function appears to be written
> properly, but does not return anything.
>
> Any help in debugging it would be appreciated.
>
> Ideally, I would like to send a date-time list in the form {y,m,d,h,m,s} to
> the function and have the Julian Day returned.
>
> Thanks for your help - Kurt
>
> (* This function computes the Modified Julian Day from a \
> system formatted date. Domain is restricted to Greogorian dates. \
> Source: Meeus. 1998. Chap. 7. Astronomical Alogrithms. *)
> (* fractionalize the day value *)
>
> JulianDayModified[y_, m_, d_, h_, m_, s_] := (
>  B = 2 - IntegerPart[y/100] + IntegerPart[IntegerPart[y/100]/4];
>  d = d + ((m * 60 )/ ( 24 * 60 )) + ((s * 3600)/(24 * 3600));
>  JD = IntegerPart[(365.25*(y + 4716))] +
>  IntegerPart[(30.6001*(m + 1 ))] + d + b - 1524.5;
>  MJD = JD - 2400000.5;
>  MJD
>  )
>
> JulianDayModified[2010, 1, 1, 12, 0, 0]
>
> Returns the string "
> JulianDayModified[2010, 1, 1, 12, 0, 0]"
>
> and not the computed date
>
> Also tried it this way with the Module statement with no change in the
> result:
>
> JulianDayModified[y_, m_, d_, h_, m_, s_] := Module[{B, JD, MJD},
>  B = 2 - IntegerPart[y/100] + IntegerPart[IntegerPart[y/100]/4];
>  d = d + ((m*60)/(24*60)) + ((s*3600)/(24*3600));
>  JD = IntegerPart[(365.25*(y + 4716))] +
>  IntegerPart[(30.6001*(m + 1))] + d + b - 1524.5;
>  MJD = JD - 2400000.5;
>  MJD
>  ]
>

--
Best
Herman
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```

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