From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Brand <michael.ch.brand@gmail.com>
Subject: Re: Difference between two rows
Date: Sun, 1 Jun 2014 13:57:09 +0200
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To: Cecil Westerhof <cldwesterhof@gmail.com>
Cc: Org Mode <emacs-orgmode@gnu.org>

Hi Cecil

On Sun, Jun 1, 2014 at 1:38 PM, Cecil Westerhof <cldwesterhof@gmail.com> wrote:
> I like to calculate in a table the difference between the value in a field
> in the current row and the previous field. How would I do that?
>
> Something like:
> |-------+------------|
> | value | difference |
> |-------+------------|
> |    12 |            |
> |    15 |          3 |
> |    83 |         68 |
> |    87 |          4 |
> |    85 |         -2 |
> |-------+------------|

For such cases I prefer vlen():

#+TBLFM: $2 = if(vlen(@II..@0) == 1, string(""), $1 - @-1$1); E

Michael