When I calculate the mean of cigs in the dataset bwght using: mean(bwght$cigs), i get a number 2.08.

Only 212 of the 1388 women in the sample smoke (and 1176 does not smoke):

summary(bwght$cigs>0) gives the result:

Mode FALSE TRUE NA's logical 1176 212 0

I'm asked to find the average of cigs among the women who smoke (the 212).

I'm having a hard time finding the right syntax for excluding the non smokers = 0 I have tried:

mean(bwght$cigs| bwght$cigs>0)

mean(bwght$cigs>0 | bwght$cigs=TRUE)

if (bwght$cigs > 0){ sum(bwght$cigs) }

x <-as.numeric(bwght$cigs, rm="0") mean(x)

But nothing seems to work! Can anyone please help me??

Thanks in advance - Maria