[R] turning an element of list into a vector

[Jim Lemon]

On 01/17/2010 04:05 AM, alessia matano wrote:
> Dear all,
>
> I am trying to apply the sapply function on a list, which comes out
> from a matrix of 25 rows and two columns, so that each element of the
> list, is a two column element. In my function within sapply, say f,  I
> would like each element of the list to become a vector so that I can
> transpose it (in a way to let it be a column vector with two rows) and
> then perform a row*column multiplication. But actually it cannot work
> it out.
>
Hi Alessia,
Your description of the problem is a bit hard to understand. It seems 
that you want to make a list out of a 25x2 matrix (amat):

amat.list<-list()
for(i in 1:dim(amat)[1]) amat.list[[i]]<-amat[i,]

Then you can sapply on the list:

sapply(amat.list,function(x) x[1]*x[2])

but this seems a very roundabout way to get the row products of the matrix.

Jim