How do I get a formula to fill multiple cells in a column

What you are describing is sometimes called fill or autofill.

Here is an explanation in the Numbers User Guide for Mac.

Autofill cells in Numbers on Mac - Apple Support

Enter a formula in a cell and then use autofill to "fill" it into the other cells in the column (or row).

If you haven't already had a look at the User Guide, you might consider doing so no. It is full of helpful material. It is always available at Help > Numbers Help in your menu.

Help > Formulas and Functions Help can also be very useful. It contains lots of examples showing how to use formulas.

SG

I believe Excel has formulas that will do that (you put a formula in one cell and it fills answers into an array of cells). I can't think of where I saw it to look it up and give it a name. Numbers does not have this feature, unless it is a recent addition they didn't mention. Regardless, it is usually pretty easy to create the necessary formula for the array of cells and copy/paste it into them. If you provide the formula and what you want as the result(s), we might be able to help.

That sounds like a regular formula, nothing special about arrays. If the one column is A, the second is B, and the one with the formula is C, then the formula in C is

=A+B

or

=A-B

or

=B-A

depending on what you want as the result.

Use that in all the cells in C that need the formula. Put it in C2 and drag-fill down to the bottom of the column or put it in C2, copy cell C2, select the other cells, paste.

Hi Mike,

You wrote:

"What I would like to do is either add or subtract one column from the other and have the results appear in the third column."

That is somewhat ambiguous, and leaves several possible interpretations:

Will the formula be required to choose which of the three possible actions (A+B, A-B or B-A) is to be taken in a particular row?

If so, what information is to determine which action is to be taken?

When that action is determined for the cell in C3, for example, do all the other rows of column C perform the same action as in C3?

Or is the action in each row independent of what action takes place in C3?

Will that action require the same information as the formula in C3, or will its action depend on a different set of information?

Regards,

Barry