Problem with date calculations in a table

Problem with date calculations in a table

[Nick Dokos]

I've been trying to make a table with the following structure: column 1
contains either a date or is empty; column 2 contains a date that's
calculated from the corresponding date in column 1 (if column 1 contains
a date) or is empty (if column 1 is empty). In the example below, column
2 is supposed to be the date 12 hours or 0.5 days after the date in
column 1 (assuming that it is non-empty).

I have tried various formulas as shown in the tables below where row 1
contains a date in column 1 and row 2 is supposed to be empty:


| start                  | ETA (start + 12 hrs)       |
|------------------------+----------------------------|
| <2008-08-14 Thu 18:15> | <2008-08-15 Fri 06:15>     |
|                        | <+1-01-01 Sat> ? 0 + 0.5 : |
#+TBLFM: $2=(date($1)?$1+0.5:string(""))


| start                  | ETA (start + 12 hrs)                                    |
|------------------------+---------------------------------------------------------|
| <2008-08-14 Thu 18:15> | <2008-08-14 Thu 06:15> ? <2008-08-14 Thu 06:15> + 0.5 : |
|                        |                                                         |
#+TBLFM: $2=($1?$1+0.5:string(""))


| start                  | ETA (start + 12 hrs)                                         |
|------------------------+--------------------------------------------------------------|
| <2008-08-14 Thu 18:15> | 733269.76 != <+1-01-01 Sat> ? <2008-08-14 Thu 06:15> + 0.5 : |
|                        |                                                              |
#+TBLFM: $2=(date($1)!=date(0)?$1+0.5:string(""))


| start                  | ETA (start + 12 hrs)            |
|------------------------+---------------------------------|
| <2008-08-14 Thu 18:15> | <2008-08-15 Fri 06:15>          |
|                        | <+1-01-01 Sat> != 0 ? 0 + 0.5 : |
#+TBLFM: $2=(date($1)!=date(<+1-01-01 Sat>)?$1+0.5:string(""))



but as you can see, there is no formula that gets both rows right. This
is a subset of all the trials that I have done: none seems to work. I'm
almost certain that the error (if it is indeed an error and not my own
stupidity) lies with calc-eval, not with org-table, but I am just not
ready to wade into those waters yet.

If somebody has a different formula, a work-around for any of the above
or some related formula, or can give me the proper head-whack to point
me in the right direction, I'd appreciate it very much.

BTW, I tried the if(a,b,c) form of the conditional as well, but it does
not make any difference afaict: they seem to be entirely
equivalent. That's what I would have expected, but desperate situations
call for desperate measures!-)

Thanks,
Nick

Version info:
Linux 2.6.24-19-generic #1 SMP Fri Jul 11 23:41:49 UTC 2008 i686 GNU/Linux
GNU Emacs 23.0.60.1 (i686-pc-linux-gnu, GTK+ Version 2.12.9) of 2008-07-01
Org-mode version 6.06b

RE: Problem with date calculations in a table

[Chris Randle]

Nick Dokos wrote:
> I've been trying to make a table with the following structure: column
> 1 contains either a date or is empty; column 2 contains a date that's
> calculated from the corresponding date in column 1 (if column 1
> contains a date) or is empty (if column 1 is empty). In the example
> below, column 2 is supposed to be the date 12 hours or 0.5 days after
> the date in column 1 (assuming that it is non-empty).     

I had problems getting date arithmetic to work in tables. I posted my
findings and solutions here:

http://article.gmane.org/gmane.emacs.orgmode/6536/

Don't know if it will fix your problem (too lazy to try!) but I suspect
it will.

-- 
Chris Randle
Org-mode 6.06b - Emacs 22.1.1 - Windows XP

Re: Problem with date calculations in a table

[Nick Dokos]

Chris Randle <chris@amlog.co.uk> wrote:

> Nick Dokos wrote:
> > I've been trying to make a table with the following structure: column
> > 1 contains either a date or is empty; column 2 contains a date that's
> > calculated from the corresponding date in column 1 (if column 1
> > contains a date) or is empty (if column 1 is empty). In the example
> > below, column 2 is supposed to be the date 12 hours or 0.5 days after
> > the date in column 1 (assuming that it is non-empty).     
> 
> I had problems getting date arithmetic to work in tables. I posted my
> findings and solutions here:
> 
> http://article.gmane.org/gmane.emacs.orgmode/6536/
> 
> Don't know if it will fix your problem (too lazy to try!) but I suspect
> it will.
> 

It did! I don't understand the details yet but the following seems to do
what I want:

| start                | ETA (start + 12 hrs)   |
|----------------------+------------------------|
| 2008-08-14 Thu 18:15 | <2008-08-15 Fri 06:15> |
|                      |                        |

#+TBLFM: $2=(date(<$1>) ? <$1>+0.5 : string(""))

The date in the first column can be just a string as above, a passive
date or an active date (the file is not in the agenda list so I don't
really have to worry about active dates).

Thanks very much,
Nick

RE: Problem with date calculations in a table

[Stephan Schmitt]

Nick Dokos wrote:
> Chris Randle wrote:
>> I had problems getting date arithmetic to work in tables. I posted my
>> findings and solutions here:
>> 
>> http://article.gmane.org/gmane.emacs.orgmode/6536/
>> 
>> Don't know if it will fix your problem (too lazy to try!) but I suspect
>> it will.
>> 
> It did! I don't understand the details yet but the following seems to do
> what I want:
> 
> | start                | ETA (start + 12 hrs)   |
> |----------------------+------------------------|
> | 2008-08-14 Thu 18:15 | <2008-08-15 Fri 06:15> |
> |                      |                        |
> 
> #+TBLFM: $2=(date(<$1>) ? <$1>+0.5 : string(""))
> 
> The date in the first column can be just a string as above, a passive
> date or an active date (the file is not in the agenda list so I don't
> really have to worry about active dates).
> 
> Thanks very much,
> Nick
> 
> 

Hi,

I tried it, too, but got the same time (6:15) when adding 
1.0 or 2.0.
how bizarre!


| start                | ETA (start + 48 hrs)   |
|----------------------+------------------------|
| 2008-08-14 Thu 18:15 | <2008-08-16 Sat 06:15> |
|                      |                        |
#+TBLFM: $2=(date(<$1>) ? <$1>+2.0 : string(""))

Greetings,
	Stephan