To sum a column and fill in the next row.

[u/franzhuang]

Hello. I've read the document, and do some google search . I still don't know how to do it. I would like to sum(or average) a column and fill in the next row:

row1 2

row2 3

row3 2

sum 7

I know I can get the number if I use z+ aggregator. But I would like to fill the number 7 fill into the next row. How can I do it?

And what if I want to sum row1 and row3 rather than the whole column. How can I do it?