 Here is another option using plyr:
 
library(plyr)
creek <- read.csv("creek.csv")
 library(ggplot2)
 creek[1:10,]
 colnames(creek) <- c("date","flow")
 creek$date <- as.Date(creek$date, "%m/%d/%Y")
 ddply(creek,"year",summarise,MED=median(flow),MEAN=mean(flow),SD=sd(flow),MIN=min(flow))

Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA
http://www.fws.gov/redbluff/rbdd_jsmp.aspx



>________________________________
>From: Pascal Oettli <kridox@ymail.com>
>To: Janesh Devkota <janesh.devkota@gmail.com> 
>Cc: r-help@r-project.org 
>Sent: Thursday, January 31, 2013 11:52 PM
>Subject: Re: [R] Summary of data for each year
>
>Hello,
>
>One possibility is:
>
>> creek <- read.csv("creek.csv")
>> colnames(creek) <- c("date","flow")
>> creek$date <- as.Date(creek$date, "%m/%d/%Y")
>> creek <- within(creek, year <- format(date, '%Y'))
>
>> with(creek, aggregate(flow, by=list(year=year), summary))
>
>HTH,
>Pascal
>
>
>Le 01/02/2013 16:32, Janesh Devkota a écrit :
>> Hello All,
>>
>> I have a data with two columns. In one column it is date and in another
>> column it is flow data.
>>
>> I was able to read the data as date and flow data. I used the following
>> code:
>>
>> creek <- read.csv("creek.csv")
>> library(ggplot2)
>> creek[1:10,]
>> colnames(creek) <- c("date","flow")
>> creek$date <- as.Date(creek$date, "%m/%d/%Y")
>>
>> The link to my data is https://www.dropbox.com/s/eqpena3nk82x67e/creek.csv
>>
>> Now, I want to find the summary of each year. I want to especially know
>> mean, median, maximum etc.
>>
>> Thanks.
>>
>> Janesh
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@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.
>>
>
>______________________________________________
>R-help@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.
>
>
>
	[[alternative HTML version deleted]]

