# Re: [R] Help w/ matrix calc

From: Adaikalavan Ramasamy <ramasamy_at_cancer.org.uk>
Date: Thu 29 Jul 2004 - 23:04:29 EST

[,1] [,2] [,3]

```[1,]    1    5    9
[2,]    2    6   10
[3,]    3    7   11
[4,]    4    8   12

```

> apply(m, 1, mean) # row means

[1] 5 6 7 8

> apply(m, 2, mean) # column means

[1] 2.5 6.5 10.5

Replace 'mean' with 'var' if you want variances instead.

On Thu, 2004-07-29 at 12:38, eesteves@ualg.pt wrote:
> Dear All,
> Help is needed! I have a matrix with frequencies of fish larvae per length
> class (var. sl) and age-group (var. median.no) obtained with
>
> >k<-table(cut(sl,(5:22)),median.no)
> >k[2:5,1:5] #to ilustrate k
>
> 4 5 6 7
> (6,7] 3 1 0 0
> (7,8] 3 0 1 0
> (8,9] 3 4 3 5
> (9,10] 3 15 7 13
>
> from this matrix I would like to obtain the mean age per length class i.e.
> vector of line means. How can I do this? If, instead of the means I wanted the
> variances, how could I do it?
> Thanks in advance,
> Eduardo Esteves

>
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R-help@stat.math.ethz.ch mailing list
https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 29 23:14:38 2004

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