How to Auto Fill in Excel 2013 with keyboard shortcuts

Since I was analysing an awful lot of data, this came really hand.

The auto fill option is very useful to drag across cells and fill them with a formula.

Just select the first number (the cell you would like to extend, here: =AVERAGE(B1:B3)) and use CTRL+SHIFT to expand the selection onto the cells you would like to fill.
Like this:

Then you press CTRL+R and it looks like this:

Now excel calculates the average for each column.
However, it is different for other directions of selections, you have to press CTRL+D(own) to fill downwards or CTRL+L(eft) or CTRL+U(up).

See here where I found this neat trick:

http://superuser.com/a/270028
http://superuser.com/a/270160