Formula - return bottom non-blank value in a range

[MisterProzilla]

Hi there,

I have a column which holds a running total of hours taken. So, for example, the user enters a number of hours in cell L50, then the formula below, which sits in N50, deducts that number from a running total above in column N.

=IF(L50<>"",IF(SUM($N$27:$N49)>0,SMALL($N$27:$N49,1)-IF($M50<>"",$M50,0),$F$22-M50),"")

The issue is that this formula was built on the assumption that hours taken would always be positive numbers and therefore the figure would always be reducing. The problem is that I sometimes need to enter negative figures to balance things out, and so the SMALL part of the formula below is causing problems, as it's looking for the smallest figure in the cells above it, whereas I need it to find the bottom-most non-blank value.

So, for example, with 50 hours remaining, I enter -5 in column L to add a few hours back on, taking it to 55. I then enter -10 in the cell below, but it now picks the original 50 up as the smallest figure in the above range, resulting in 60 where it should be 65.

I hope this makes sense. Basically, I need to replace the SMALL component with something that finds the lowest (position, not value) non-blank cell in the range $N$27:$N49. I can't use the most recent, as not all values have dates attached.


Thanks in advance for your help

 

[Jonmo1]

Finding the furthest down 'numeric' value, try

LOOKUP(9.99999999999999E+307,$N$27:$N49)

 

[MisterProzilla]

Perfect, thanks very much

How does that even work, just out of curiosity?

 

[Jonmo1]

You're welcome..
9.99999999999999E+307 is just the scientific notation for the largest number allowed in a cell, also called Bignum.

Lookup assumes your data is sorted in ascending order (it doesn't verify if it actually is or not, it just proceeds as if it is).
Lookup is looking for the largest value that is less than or equal to the lookup value.
The BigNum guarantees that there will be no numbers larger than the lookup value.
So it must look at all the numbers because it doesn't know if the next number is greater or not. So it has to check them all.
It doesn't really look at all of them, because it's assumed to be sorted ascending, it does a Binary search where it cuts the ranges in half and looks at the last one. It then proceeds with a process of elimination.
When it looks at the last number in the range, it will NOT be greater than the lookup value.
So it assumes the last value IS the largest number (because it assumes the data is sorted ascending).

 

[MisterProzilla]

Aha, and computers think they're so smart

I think I got most of that, apart from the bit about cutting the ranges in half


Thanks again

 

[Jonmo1]

Cutting ranges in half...

original list of numbers
1 2 3 4 5 6 7 8 9 10

Lookup cuts it in half, and looks at the last number of each half..
1 2 3 4 5 (Is 5 greater than the lookup value?)
If No, then it looks at 6 7 8 9 10 (is 10 greater....
If Yes, then it looks at 6 7 8 (is 8 greater...
etc..