> -----Original Message-----
> When I try to apply mean to a list, I get the answer :
>
> argument is not numeric or logical: returning NA
>
Example:
l4 <- list(1:4)
class(l4) #not numeric or logical ...
mean(l4) #same error
#a list is not a number, a logical (TRUE/FALSE) or a vector or array of either
of those. So mean() can't handle it unaided and tells you what it needs.
#But if your list is a list of numeric objects, unlist will often work.
unlist(l4) #a numeric vector
mean( unlist(l4) ) #no problem
l.some <- list(matrix(1:4, ncol=2), 3:7)
l.some
unlist(l.some) #a numeric vector
mean( unlist(l.some) ) #works
#But a) magic has limits and b) if you want averages, maybe you should not be
using a list? A vector would save hassle if it fits ...
S Ellison
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