Alignment of numbers in tables with `nan' in some table cells

[Christian Schlauer <cs-muelleimer-rubbish.bin@arcor.de>]

Hello Carsten, hello list!

This is about alignment of numbers in tables. Say I have three columns
with data (the first three columns). Then I do calculations on them
(the last two columns).

Columns 2 and 3 are "complete" -- I have data in each field, so there
is always some useful result in column 4, as $4=$2-$3. But column 5 is
$5=$1-$4, and in column 1 there are some empty fields where data are
missing, unfortunately. That leads to a negative value of -6 in line
3, column 5:

| data 1 | data 2 | data 3 | result 1 | result 2 |
|--------+--------+--------+----------+----------|
|     23 |     25 |     17 |        8 |       15 |
|        |     24 |     18 |        6 |       -6 |
#+TBLFM: $4=$2-$3::$5=$1-$4

Now, a negative value doesn't make sense in my real table. So instead
of printing a nonsensical value, I'd prefer something else there. I
remembered that MATLAB has `NaN', and Calc has that, too: `nan', see
(info "(calc)Infinities"). So I put `nan' in line 3, column 1, and
recalculate the above table:

| data 1 | data 2 | data 3 | result 1 | result 2 |
|--------+--------+--------+----------+----------|
| 23     |     25 |     17 |        8 | 15       |
| nan    |     24 |     18 |        6 | nan      |
#+TBLFM: $4=$2-$3::$5=$1-$4

It's almost perfect! It is clear that a result for column 5 in line 3
does not exist as there are no data in column 1 of that line. The only
thing that is not perfect is that the alignment in columns 1 and 5 is
messed up due to `nan'.

Could this be fixed?

Regards,
-- 
Christian Schlauer