[R] Vector from Matrix

[David Winsemius]

On Jan 29, 2010, at 11:25 AM, Thiem Alrik wrote:

> Dear Mailing List Members,
>
> the problem I've been grappling with für quite some time now is the  
> following:
>
> I have a 100 rows x 200 columns matrix.
>
> data.set <- matrix(rnorm(20000, 100, 200))

I am guessing that you wanted to type:
data.set <- matrix(rnorm(20000), 100, 200)

>
> Now I would like to get a vector of length 100 which collects the  
> values from the following procedure:
>
> Take the sum of the minima of the two values from each row of  
> columns 1 and 101, and divide it by the sum of column 101.

If so, then this should be step 1:

sum( pmin(data.set[,1], data.set[,101]))/sum(data.set[,101])

> Do the same for column 2 and 102, 3 and 103 and so on.

Perhaps (runs without error but unverified):

sapply(1:100, function(x) sum(pmin(data.set[,x], data.set[,100+x]))/ 
sum(data.set[,100+x]))


> Thanks a lot for your help.
>
> Alrik
>
> *******************************************
> Alrik Thiem
> Research Assistant
>
> WEC E17


David Winsemius, MD
Heritage Laboratories
West Hartford, CT