org mode - add formula to generate delta column

Question

How can I get below result with org table formula? The number of rows maybe too many, so doing it line by line is not good way.

For example:

@1$2 = @1$1 - @1$1
@2$2 = @2$1 - @1$1
@3$2 = @3$1 - @2$1
...

| x | delta |
|---+-------|
| 2 |     0 |
| 3 |     1 |
| 5 |     2 |
| 1 |    -4 |
| 7 |     6 |

Answer 1

Using Calc’s logical operations to handle the first row:

| x | delta |
|---+-------|
| 2 |     0 |
| 3 |     1 |
| 5 |     2 |
| 1 |    -4 |
| 7 |     6 |
#+tblfm: $2=@# < 3 ? 0 : $1-@-1$1

Explanation:

• Org-tables understand Calc expressions (see (info "(org) Formula syntax for Calc")). The if expression uses the syntax condition ? then-part : else-part.
• @#, the current row's index number, is being substituted before calc-eval. @# < 3 tests whether the current row's index is less than 3.
• $1 refers to the current row in column 1. @-1$1 takes the value in column 1 with current row's index minus 1 (the cell one row above). The else part subtracts the value in the cell above from the value in the current row's cell.

Answer 2

As follows:

| x | delta |
|---+-------|
| 2 |     0 |
| 3 |     1 |
| 5 |     2 |
| 1 |    -4 |
| 7 |     6 |
#+TBLFM: @2$2=0::@3$2..@>$2=@0$1-@-1$1

The entry @2$2, row 2 column 2, has to be set separately. Otherwise @3$2..@>$2, rows 3 to last, column 2, is set to @0$1 (current row, column 1) minus @-1$1 (previous row, column 1). Details of mechanisms for referencing different cells may be found in the Org Mode info page, under The spreadsheet, available via C-h i or at the online version