AutoFill behaviour

[Andy Brown]

Dragging a single 1 downwards results in a range of 1s. The same action with
CTRL thrown in gives incrementation by 1. This is AFAIK fairly default
behaviour.

I tried two test sequences (selected them entirely then dragged down), as
follows -

1 - 1 - 2 - 2 - 3 - 3 ; 1 - 1 - 1 - 2 - 2 - 2.

In both cases, the first thing XL did was add on 20%. For the first
sequence, XL then repeatedly added on 0.45714285714286 ; for the second,
0.25714285714286.

Could a guru please shed some light on what the maths/sequence here is?

TIA,
Andy

 

[Dave Peterson]

If you rightclick on the autofill button and drag, then when you let go, you'll
be prompted for what kind of fill.

It looks like if you just drag, then excel will use Linear Trend. (At least
with these two sequences.)

(If I'm not sure what excel will use, I'll always (at least the second time)
rightclick and drag and choose the one I want.)