'Lock' part of formula when copying from one cell to another
Is there a way to control which variables in a formula get incremented when you use auto-fill in a Google Docs spreadsheet?
What I'm trying to do is convert a column of counts to a column of proportions. So, for the first cell in the proportions columns, I wrote "=E2/sum(E2:E17)". When I drag down the box in the lower right corner to auto-fill the other cells in the column with the appropriate formulas, I get the unintended effect that "sum(E2:E17)" does not stay constant -- in the next cell it is "sum(E3:E18)" and so on. What I'm looking for is a way to make auto-fill leave that part of the formula unchanged.