Thought I was getting the hand of array functions. Clearly not....

Can I use an array function with a set of discontiguous cells, for example
(A1,A3,A5,A7,A9) rather than A1:A10?

If not can someone suggest away of finding the average value of a set of
discontiguous cells, some of which may have numbers, others may have an error
code. (Not sure if this is relevent but I have specified any error code to be
#N/A to ensure that I can still use the data set for a line chart, and not
return a zero value for a cell with errors)?

Is there a way without using an array function?