Good day everyone. I have a large dataset of 1 min wind speeds covering 5 years. How can I make an array of maximum daily values? The vectors I have are: 'VDATE' with dates in format '%Y-%m-%d' (like '1992-10-28') and 'WS' with wind speed data (same number of elements as VDATE). I want an array with 2 columns: Max daily wind speed and corresponding day. Has anyone got an elegant way of doing that? (My background is in C++ I would tend to use loops but that is not very elegant in R, isn't it?) Augusto -------------------------------------------- Augusto Sanabria. MSc, PhD. Mathematical Modeller Risk Research Group Geospatial & Earth Monitoring Division Geoscience Australia (www.ga.gov.au) Cnr. Jerrabomberra Av. & Hindmarsh Dr. Symonston ACT 2609 Ph. (02) 6249-9155
Assuming VDATE is a character vector this produces
a zoo time series object.
library(zoo)
z <- aggregate(zoo(WS), as.Date(VDATE), max)
coredata(z) and time(z) are the data vector of maximums and
corresponding times, respectively.
The R command:
vignette("zoo")
gives an introduction to zoo.
Aside from zoo you could check out ?tapply, ?by and ?aggregate .
On 1/16/06, Augusto.Sanabria at ga.gov.au <Augusto.Sanabria at ga.gov.au>
wrote:>
> Good day everyone.
>
> I have a large dataset of 1 min wind speeds
> covering 5 years.
>
> How can I make an array of maximum daily values?
>
> The vectors I have are: 'VDATE' with dates in format
> '%Y-%m-%d' (like '1992-10-28') and 'WS' with wind
speed data
> (same number of elements as VDATE).
>
> I want an array with 2 columns: Max daily wind speed and
> corresponding day.
>
> Has anyone got an elegant way of doing that?
> (My background is in C++ I would tend to use loops
> but that is not very elegant in R, isn't it?)
>
> Augusto
>
>
>
> --------------------------------------------
> Augusto Sanabria. MSc, PhD.
> Mathematical Modeller
> Risk Research Group
> Geospatial & Earth Monitoring Division
> Geoscience Australia (www.ga.gov.au)
> Cnr. Jerrabomberra Av. & Hindmarsh Dr.
> Symonston ACT 2609
> Ph. (02) 6249-9155
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>
Thank you Gabor, the 'aggregate' function
operating on zoo(WS) does the job beautifully!
'zoo' has a lot of other goodies too, great
package (thanks for that too).
Cheers,
Augusto
--------------------------------------------
Augusto Sanabria. MSc, PhD.
Mathematical Modeller
Risk Research Group
Geospatial & Earth Monitoring Division
Geoscience Australia (www.ga.gov.au)
Cnr. Jerrabomberra Av. & Hindmarsh Dr.
Symonston ACT 2609
Ph. (02) 6249-9155
-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com]
Sent: Tuesday, 17 January 2006 4:32 PM
To: Sanabria Augusto
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Calculation of daily max
Assuming VDATE is a character vector this produces
a zoo time series object.
library(zoo)
z <- aggregate(zoo(WS), as.Date(VDATE), max)
coredata(z) and time(z) are the data vector of maximums and corresponding
times, respectively.
The R command:
vignette("zoo")
gives an introduction to zoo.
Aside from zoo you could check out ?tapply, ?by and ?aggregate .
On 1/16/06, Augusto.Sanabria at ga.gov.au <Augusto.Sanabria at ga.gov.au>
wrote:>
> Good day everyone.
>
> I have a large dataset of 1 min wind speeds
> covering 5 years.
>
> How can I make an array of maximum daily values?
>
> The vectors I have are: 'VDATE' with dates in format
'%Y-%m-%d' (like
> '1992-10-28') and 'WS' with wind speed data (same number of
elements
> as VDATE).
>
> I want an array with 2 columns: Max daily wind speed and corresponding
> day.
>
> Has anyone got an elegant way of doing that?
> (My background is in C++ I would tend to use loops
> but that is not very elegant in R, isn't it?)
>
> Augusto
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
>