R help - Nov 2012 - Calculateing means

Dear List,

I have a data matrix with 570 columns containing 95 (samples) with 6 replicates
each.
How can I calculate the mean of the replicates for 95 samples?
Thank you.


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?aggregate will do it.

x <- data.frame( height= c(50, 174, 145, 200, 210, 140, 175),
age_group=c(1,2,2,1,1,2,1),
                     ville= c(1,2,3,1,2,3,1))

aggregate(x$height,list(x$age_group, x$ville), mean)

or have a look at the plyr or datatable packages.

John Kane
Kingston ON Canada

> -----Original Message-----
> From: skhan30 at nshs.edu
> Sent: Fri, 16 Nov 2012 15:58:17 -0500
> To: r-help at r-project.org
> Subject: [R] Calculateing means
> 
> 
> Dear List,
> 
> I have a data matrix with 570 columns containing 95 (samples) with 6
> replicates each.
> How can I calculate the mean of the replicates for 95 samples?
> Thank you.
> 
> 
> The information contained in this electronic e-mail transmission and any
> attachments are intended only for the use of the individual or entity to
> whom or to which it is addressed, and may contain information that is
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> I have a data matrix with 570 columns containing 95 (samples) 
> with 6 replicates each.
> How can I calculate the mean of the replicates for 95 samples?
Write a function that calculates the sample means for a vector of 95
observations and then use apply() to apply that function to the whole matrix.

S

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