[R] dot products

[R. Michael Weylandt <michael.weylandt@gmail.com>]

as.matrix(df) %*% vec

Michael 

On Mar 7, 2012, at 3:14 PM, Alexander Shenkin <ashenkin at ufl.edu> wrote:

> Hello,
> 
> I need to take a dot product of each row of a dataframe and a vector.
> The number of columns will be dynamic.  The way I've been doing it so
> far is contorted.  Is there a better way?
> 
>    dotproduct <- function(dataf, v2) {
>        apply(t(t(as.matrix(a)) * v2),1,sum) #contorted!
>    }
> 
>    df = data.frame(a=c(1,2,3),b=c(4,5,6))
>    vec = c(4,5)
>    dotproduct(df, vec)
> 
> 
> thanks,
> allie
> 
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