[R] getting a weighted average from a table

[David Winsemius]

On May 7, 2010, at 9:42 AM, SHANE MILLER, BLOOMBERG/ 731 LEXIN wrote:

> Hi,
>
> I have a very simple request (I think).
> I have a vector/array,
>
>> c <- c(1.3,1.2,1,3.3,3.3,5.1,1.1,1.2,0)
>
> I produce a reverse sorted table/histogram with it,
>
>> t = rev(sort(table(c))
>> t
>  c
>  3.3 1.2 5.1 1.3 1.1   1   0
>    2   2   1   1   1   1   1
>
> I would now like to get the labels "3.3 1.2 5.1 1.3 1.1   1   0"
> into its own vector and the # of counts "2   2   1   1   1   1   1"

 > names(t)
[1] "3.3" "1.2" "5.1" "1.3" "1.1" "1"   "0"
 > as.numeric(names(t))
[1] 3.3 1.2 5.1 1.3 1.1 1.0 0.0
 > unname(t)
[1] 2 2 1 1 1 1 1


> so I can calculate weighted averages. So if I can get the labels into
> a vector l and the counts into a vector n,
>
>  l <- c(3.3,1.2,5.1,1.3,1.1,1,0);
>  n <- c(2,2,1,1,1,1,1);
>
> for(i=0;i<7;i++)
>  total = l[i]*n[i]
> total = total / sum(n)     <- this is the weight average
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David Winsemius, MD
West Hartford, CT