Dear All,
Help is needed! I have a matrix with frequencies of fish larvae per length 
class (var. sl) and age-group (var. median.no) obtained with 

>k<-table(cut(sl,(5:22)),median.no)
>k[2:5,1:5] #to ilustrate k

        4  5  6  7 
(6,7]   3  1  0  0
(7,8]   3  0  1  0
(8,9]   3  4  3  5
(9,10]  3 15  7 13

from this matrix I would like to obtain the mean age per length class i.e. 
vector of line means. How can I do this? If, instead of the means I wanted the 
variances, how could I do it?
Thanks in advance,
Eduardo Esteves


