Sum org-mode table column based on other column

Question

I have this org-mode table:

| Category         | Category Budget | Needs Transfer |
|------------------+-----------------+----------------|
| Rent             |            3000 | t              |
| Internet         |             125 | t              |
| Food             |            1000 |                |
| Coffee           |             500 |                |
| Cellphone        |             120 | t              |
| Cigarettes       |             100 |                |
| Total            |            9945 |                |

I want the "Total" row, in the "Needs Transfer" column, to show the sum of all of the budgets that have "t" in their "Needs Transfer" column.

I already tried this solution to no avail:

@>$3 = '(apply '+ '(org-lookup-all "t" '(@2$3..@-1$3) '(@2$2..@-1$2) 'string=));E

Answer 1

You almost have it: you have quoted the org-lookup-call which prevents its evaluation; and you need to convert the strings in the second list to numbers in order to add them together. This works for me:

#+TBLFM: @>$3 = '(apply '+ (org-lookup-all "t" '(@2$3..@-1$3)  (mapcar #'string-to-number '(@2$2..@-1$2)) 'string=));E

Answer 2

You may use the orgtbl-aggregate package available on http://melpa.org

Give a name to your table, for instance

#+name: mytable

Then create an aggregation block with C-c C-x i

#+BEGIN: aggregate :table "mytable" :cols "'Needs Transfer' vsum('Category Budget')"
| 'Needs Transfer' | vsum('Category Budget') |
|------------------+-------------------------|
| t                |                    3245 |
|                  |                   11545 |
#+END:

You get the sum for rows with t, and as a bonus the sum of rows without t.