annual maximum value

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)

 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...