[R] Convert date to decimal days

[cls59]

Hello all,

I have a quick question about formatting date strings..

I am currently debugging some Matlab code someone else wrote and since it is
so bad that I have to go through it line by line I figured that I would just
rewrite the thing in R.

The code produces plots of wave spectra with decimal days since the Epoch as
the x axis and wave period as the Y axis. I am able to convert the date
stamp in the input file to a POSIXct object with the following call:

date = as.POSIXct(header[[1]][2],tz='GMT',format='%Y%m%d_%k')
date
"2008-07-11 03:00:00 GMT"

So every thing looks groovy, using as.double(date) gives me the number of
seconds since the epoch which reproduces the correct date when fed to date
-u -r on the command line.

However, I can't seem to find a clean way of converting the date to decimal
days since the epoch. Using

as.double(date)/86400

Gives:

14071.12

Which is a catastrophic loss of significance, the number should be 14071.125

I tried playing around with the format command to see if I could get R to
format the date differently, but no luck.

Any suggestions?

-Charlie
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