On Sun, 2 Sep 2012, Wolfgang Schuster wrote:

>
> Am 02.09.2012 um 17:59 schrieb Aditya Mahajan <adityam@umich.edu>:
>
>> Hi,
>>
>> On Edward Tufte's website, there is a discussion on zebra coloring in tables[1]. One of the suggestion is to add a horizontal rule after every third line or shade three lines with one background color and the remaining three with another background color.
>>
>> Is there an easy way to do this with natural TABLEs? I can do something like:
>>
>> \setupTABLE[row][1,2,3][background=color, backgroundcolor=gray]
>> \setupTABLE[row][7,8,9][background=color, backgroundcolor=gray]
>>
>> but it requires knowing the number of lines in advance.
>>
>> Aditya
>>
>> [1]: http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0001IV
>
> Natural tables have “odd” and “even” keywords for \setupTABLE but none 
> in the way you like it.

Well, I can always change what odd and even means :) (I also realized that 
odd and even are just dummy values. I can change them to anything, and can 
in fact even turn \v!oddeven to a switch statement that returns multiple 
values)

\unprotect
\def\redefineoddeven% HACK
     {\def\v!oddeven##1% Return odd if in set 1-3, 7-9, etc. and even otherwise
         {\ctxcommand{doifelse(math.mod(##1-1,6) < 3)}\v!odd\v!even}}
\protect

\startsetups zebra:three
     \redefineoddeven
     \setupTABLE[frame=off,background=color]
     \setupTABLE[row][odd][backgroundcolor=blue]
     \setupTABLE[row][even][backgroundcolor=red]
\stopsetups

\starttext
\startTABLE[setups={zebra:three}]
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
   \NC A \NC B \NC C \NC \NR
\stopTABLE
\stoptext

> What I would do is to use a overlay in combination with metapost to 
> create the background but there is no global register to access the 
> current column/row of a cell, e.g. \currenttablecolumn (this name is 
> already used by tables) and \currenttablerow.

Thanks for the hint. It is relatively easy to access the local counter for 
a cell, and changing background colors dependon the current row works 
well.

\defineconversion
     [triadcolors]
     [blue,blue,blue,red,red,red]

\startsetups zebra:three
     \setupTABLE[frame=off,background=color]
     \setupTABLE[row][backgroundcolor={\convertnumber{triadcolors}{\getvalue{m_tabl_ntb_positive_row}}}]
\stopsetups

If I need rules, I guess I can explicitly check for the value of \m_tabl_ntb_postive_pow 
inside an overlay.

Thanks,
Aditya