Nice! Definitely much simpler and more efficient. Although I would
change it slightly to the following...

=AVERAGE(IF(ISNUMBER(D4:P4),D4:P4),IF(ISNUMBER(U4: AG4),U4:AG4))

....confirmed with CONTROL+SHIFT+ENTER.

Three reasons:

1) Your formula seems to count empty cells, whereas this syntax seems to
ignore them.

2) It's a little easier to understand.

3) It looks nicer. :)

In article ,
"
wrote:

"joshkraemer" wrote:
Here's what I want to do (but doesn't work):
{AVERAGE(IF(ISERROR(D4:P4,U4:AG4),"",D4:P4,U4:AG4) )}
[....] I want to be able to ignore all errors when calculating
an average for _multiple_(2)_ranges_

General form of the array formula (ctrl-shift-Enter):

=average(if(condition1,range1), if(condition2,range2), ...)

In your case:

=average(if(not(iserror(U2:P4)), U2:P4),
if(not(iserror(U4:AG4)), U4:AG4))

PS: Personally, I would avoid the errors within the ranges
in the first place. Makes for a less messy spreadsheet.