R help - Feb 2009 - annual maximum value

hi everyone!

hope you can help me here.

i am a new R user. what i am trying to do is to find the maximum annual
discharge from a daily record. i have a data.frame which includes date and
the discharge. somewhat like this..

10/1/1989       2410
10/2/1989       2460
10/3/1989       2890
...
...
...
12/31/2005     5730

i have been browsing through the archives and fount out about the aggregate
function and the zoo package. here's one of the codes i've tried

DF <- read.table(data[i], sep =",")  ##i have several stations to
assimilate
Date <- as.Date(as.character(DF[,3]), "%m/%d/%Y") #the date is at
the 3rd
column, obviously
library(zoo)
z <- aggregate(zoo(DF[,4]), cut(Date, "y"), max)
max.discharge <- coredata(z)
date <- time(z)

the result should somehow look like this 
11/21/1926      32600
 4/24/1927       66500
...
...
..
4/26/2005       111000

thanks for your time reading my questions,, any suggestions will be truly
appreciated...
  


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Try this:
> Lines <- textConnection("10/1/1989,2410
+ 10/2/1989,2460
+ 10/3/1989,2890
+ 12/31/2005,5730")
>
> library(zoo)
> library(chron)
> z <- read.zoo(Lines, header = FALSE, sep = ",", FUN = chron)
> aggregate(z, floor(as.numeric(as.yearmon(time(z)))), max)
1989 2005
2890 5730

See ?read.zoo, ?aggregate.zoo, ?as.yearmon, the 3 vignettes in the
zoo package and R News 4/1.

On Mon, Feb 16, 2009 at 10:11 PM, CJ Rubio <cjrubio at kongju.ac.kr>
wrote:
>
>  hi everyone!
>
> hope you can help me here.
>
> i am a new R user. what i am trying to do is to find the maximum annual
> discharge from a daily record. i have a data.frame which includes date and
> the discharge. somewhat like this..
>
> 10/1/1989       2410
> 10/2/1989       2460
> 10/3/1989       2890
> ...
> ...
> ...
> 12/31/2005     5730
>
> i have been browsing through the archives and fount out about the aggregate
> function and the zoo package. here's one of the codes i've tried
>
> DF <- read.table(data[i], sep =",")  ##i have several stations
to assimilate
> Date <- as.Date(as.character(DF[,3]), "%m/%d/%Y") #the date is
at the 3rd
> column, obviously
> library(zoo)
> z <- aggregate(zoo(DF[,4]), cut(Date, "y"), max)
> max.discharge <- coredata(z)
> date <- time(z)
>
> the result should somehow look like this
> 11/21/1926      32600
>  4/24/1927       66500
> ...
> ...
> ..
> 4/26/2005       111000
>
> thanks for your time reading my questions,, any suggestions will be truly
> appreciated...
>
>
>
> --
> View this message in context:
http://www.nabble.com/annual-maximum-value-tp22049205p22049205.html
> Sent from the R help mailing list archive at Nabble.com.
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

thank you very much for your reply.

i studied the code you gave me and tried to make adjustments to fit the
requirements that i need, thank you again.. i used the following codes:
> m <- read.table("D:/documents/5 stations/01014000.csv", sep
=",")
> z <- zoo(m[,4],as.Date(as.character(DF[,3]), "%m/%d/%Y"))
> x <- aggregate(z, cut(time(z),"y"), max)
i got the maximum values right using coredata(), my question now is, how can
i call for the complete date (yyyy-mm-dd)  and the year (yyyy) when the
maximum observation for that year was observed? 




CJ Rubio wrote:
> 
>  hi everyone!
> 
> hope you can help me here.
> 
> i am a new R user. what i am trying to do is to find the maximum annual
> discharge from a daily record. i have a data.frame which includes date and
> the discharge. somewhat like this..
> 
> 10/1/1989       2410
> 10/2/1989       2460
> 10/3/1989       2890
> ...
> ...
> ...
> 12/31/2005     5730
> 
> i have been browsing through the archives and fount out about the
> aggregate function and the zoo package. here's one of the codes
i've tried
> 
> DF <- read.table(data[i], sep =",")  ##i have several stations
to
> assimilate
> Date <- as.Date(as.character(DF[,3]), "%m/%d/%Y") #the date is
at the 3rd
> column, obviously
> library(zoo)
> z <- aggregate(zoo(DF[,4]), cut(Date, "y"), max)
> max.discharge <- coredata(z)
> date <- time(z)
> 
> the result should somehow look like this 
> 11/21/1926      32600
>  4/24/1927       66500
> ...
> ...
> ..
> 4/26/2005       111000
> 
> thanks for your time reading my questions,, any suggestions will be truly
> appreciated...
>   
> 
> 
> 
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