[R] calculating mean and s.d. from a two-column table

[Joshua Wiley]

Hi,

Peter's suggestion is more general, but for just the weighted mean,
there is a built in function you can use (I do not know of any basic
weighted standard deviation or variance functions).

dat <- data.frame(age = 1:5, no = c(21, 31, 9, 12, 6))
weighted.mean(x = dat$age, w = dat$no)

Best regards,

Josh

On Mon, Sep 27, 2010 at 9:34 AM, Jonas Josefsson
<jonas at runtimerecords.net> wrote:
> I have a two-column table as follows where age is in the 1st column and the
> number of individuals is in the 2nd.
>
> age;no
> 1;21
> 2;31
> 3;9
> 4;12
> 5;6
>
>
> Can I use mean() and sd() to calculate the mean and standard deviation from
> this or do I have to manually multiplicate 21*1+31*2 etc. / N?
>
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>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/