Sigma

**a.janmohammadi** · 11-10-2014, 09:40 AM

Hi guys
Is there a Summation Formula in Excel ? For example, a formula to calculate SIGMA of a (Xi - Yi) where Xi and Yi are each entered in a column ?

**AlanY** · 11-10-2014, 09:45 AM

don't think so.
suppose because it's so easy to take one away from the other, sum(columnA)-sum(columnB).

**a.janmohammadi** · 11-10-2014, 10:41 AM

That one IS easy. but it was just an example. What I mean is, using SIGMA for more complicated formulas where we can assign columns to variables with the subscript i
Am I clear or should upload a file?

**MrShorty** · 11-10-2014, 11:52 AM

I can't think of any "generic" sum(f(xi,yi)) function. Excel has several built in in summation functions like the =SUM(), =SUMX2PY2(), and SUMXMY2() (see complete list here: https://support.office.com/en-us/art...-US&ad=US#bm19 ). If you can arrange your f(xi,yi) so that it looks like any of the built in functions, then you can work it out that way.

IMO, the easiest and most generic way of performing summations in Excel is to add a helper column that will compute your f(xi,yi) values, then use the =SUM() function to perform the summation. I know that, for some reason, we do not like to use helper columns, but it has always seemed like the easiest way to me to perform summations.