How do I use an array formula over a whole column or varying range? - excel-formula

Question

I have a spreadsheet that I'm importing data into. I need to find the value within a column that is closest to zero. The column contains both positive and negative values, and the value closest to zero will be used in another formula. I've found an answer using an array formula, but it will only work for a fixed range (e.g. K2:K10), and the number of records imported into my sheet will vary each time I use it.
Here's what I have so far:
=INDEX(K:K,MATCH(MIN(ABS(K:K)),ABS(K:K),0))
Is there a way to apply an array formula over an entire column and just include non-zero cells other than the column title? Or possibly just cells with numerical values? Or is it possible to control the range that it applies to?

Answer 1

We can dynamically find the last cell in the range by using another INDEX/MATCH formula that is not an array:
=INDEX(K:K,MATCH(1E+99,K:K))
This will find the last cell that has a number in column K.
So we now use this as the last cell in the range:
=INDEX($K$2:INDEX(K:K,MATCH(1E+99,K:K)),MATCH(MIN(ABS($K$2:INDEX(K:K,MATCH(1E+99,K:K)))),ABS($K$2:INDEX(K:K,MATCH(1E+99,K:K))),0))
And now the formula is dynamic.
This formula is still an array formula and must be confirmed with Ctrl-Shift-Enter when exiting edit mode. If done correctly then Excel will put{} around the formula.
If as you pointed out there is a chance of deleting row 2 then all the K2 references will also be deleted.
In place of K2 we can use INDEX(K:K,2) It will now always look at the second row and will not error when row 2 is erased. So use this instead:
=INDEX(INDEX(K:K,2):INDEX(K:K,MATCH(1E+99,K:K)),MATCH(MIN(ABS(INDEX(K:K,2):INDE‌​X(K:K,MATCH(1E+99,K:K)))),ABS(INDEX(K:K,2):INDEX(K:K,MATCH(1E+99,K:K))),0))
There is nothing wrong with the Offset() function in small amounts, but it is a volatile function. Which means that it will calculate EVERY TIME excel calculate whether the data to which it is dependent has changed or not.

Answer 2

For the benefit of anyone reading this post, I ran into another issue and found a way around it. Scott Craner's answer above worked well until I ran a macro that I had for that sheet, which would delete certain rows. If row 2 got deleted, the formula would give a #REF error, because it was trying to call $K$2.
My solution was to replace $K$2 with
OFFSET(K1,1,0)
Therefore, the complete formula would be:
=INDEX(OFFSET(K1,1,0):INDEX(K:K,MATCH(1E+99,K:K)),MATCH(MIN(ABS(OFFSET(K1,1,0):INDEX(K:K,MATCH(1E+99,K:K)))),ABS(OFFSET(K1,1,0):INDEX(K:K,MATCH(1E+99,K:K))),0))
And as Scott mentioned, remember to hit Ctrl-Shift-Enter to execute the array formula.