R help - May 2010 - How to skip negative values when calculating average

I have a data frame 10 by 12 with positive and negative numbers. I  
want to select only the positive numbers and find the average.

This calculates the average of everything:
av5 <-  subset(ER9r, Day == 253, select = c (Depth1j:Depth0.75j)
av5 <- mean(av5)
I need something along the lines of "select" av5>0

Thanks in advance!

Emilija

On May 31, 2010, at 2:06 PM, ecvetano at uwaterloo.ca wrote:
> I have a data frame 10 by 12 with positive and negative numbers. I  
> want to select only the positive numbers and find the average.
>
> This calculates the average of everything:
> av5 <-  subset(ER9r, Day == 253, select = c (Depth1j:Depth0.75j)
That looks to be missing a closing paren. If so, then after fixing you  
first line try:

mean( av5[av5>0] )
> av5 <- mean(av5)
> I need something along the lines of "select" av5>0
>
> Thanks in advance!
>
> Emilija
>
> ______________________________________________
David Winsemius, MD
West Hartford, CT