Re: list of dates
- To: mathgroup at smc.vnet.net
- Subject: [mg88391] Re: list of dates
- From: "Roger Nye" <roger.nye at actuary.ch>
- Date: Sat, 3 May 2008 06:20:06 -0400 (EDT)
- References: <fvegu1$5e9$1@smc.vnet.net>
Thanks for your suggestions.
A key aspect of the problem is that the dates are a list, so I want to be
able to operate on them as a list.
The approximation of leap years does not concern me, although the year has
to be correct (i.e. 1st Jan of year xx must be xx.0, not xx-1.997).
Adapting your suggestions and after much struggle (I am new to Mathematica),
I came up with this
("date" is the list of dates input, "t" is the list of values output):
n = Length[date];
year = Transpose[Map[DateList, date]][[1]];
days = Table[DateDifference[{year[[i]]}, date[[i]]], {i, 1, n}];
t = year - 1900 + days / 365.24;
which does what I wanted (thanks).
It is however very slow. It takes a couple of minutes for 15,000 dates.
All the other software I have used for a similar calculation (Excel, Stata)
does it in a split second.
Is there a much more efficient method?
Many thanks
Roger
"Roger Nye" <roger.nye at actuary.ch> wrote in message
news:fvegu1$5e9$1 at smc.vnet.net...
> Hi,
> I have a list of dates in the format YYYY-MM-DD and I want to convert them
> to a decimal value, so 1963-01-01 goes to 63.0 and 1985-07-01 goes roughly
> to 85.5.
>
> Any suggestions on the best way to do this?
>
> Many thanks
> Roger
>
>
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