Thanks a lot to Gabor for his help with the solution
of this problem.
The solution using zoo(aggregate)
is easy to implement efficient. I have calculated
the 15min mean values of a 1min wind speed file
containing 2.9 million records x 16 columns
(size 179 MB) in just 144 seconds
(R-2.1.1
character to datettime.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Gabor
Grothendieck
Sent: Thursday, February 02, 2006 1:44 AM
To: [EMAIL PROTECTED]
Cc: r-help@stat.math.ethz.ch
Subject: Re: [R] 15-min mean values
Assume VDATE is a character vector
Good day everyone,
I want to use zoo(aggregate) to calculate
15-min mean values from a wind dataset which
has 1-min values. The data I have looks like this:
vector VDATE vector WS
1 1998-10-22:02:11 12.5
2 1998-10-22:02:12 10.1
3 1998-10-22:02:13
Assume VDATE is a character vector. If its a
factor first convert it using
VDATE - as.character(VDATE)
Lets assume we only need the times portion
and later we handle the full case which may or
may be needed.
We create a times object from the times portion of
vdate and then in the
