R help - Apr 2010 - finding weekly average...

Hi All,

I have a time series data with two continuous variables (say Var1 and Var2)
for 4 years (***not continuous, do have some breaks because of missing
data***). Something like this:

Date Var1 Var2
12/01/2004 7 0
12/01/2004 0 0
12/01/2004 0 7
12/01/2004 7 0
12/01/2004 0 7
12/01/2004 0 7
12/02/2004 0 0
...

I need to find out weekly average of var1 and var2, so that I end up with
data like:

 Week Year Var1 Var2
week1 2004 2 3
week2 2004 4 2
...
week52 2004 4 4
week1 2005 2 3
...

Can anyone help please, any help would be greatly appreciated. Thanks!

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Assume you have suitable "week" indicator and your data is stored in a
data.frame named "data." Then you get the weekly averages by

#simulate data
week <- rep(1:52,each=7)
x <- week+rnorm(52*7,)
y  <- rev(week)+rnorm(52*7)

#create data frame
data=data.frame(week,x,y)

#get weekly averages in a list
averages=unlist(lapply(split(data,week),colMeans))

#unlist averages and store the results in matrix
matrix(averages,byrow=T,ncol=dim(data)[2])

HTH,
Daniel
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