Hello,

Lua solution:

On Sun, 02 Sep 2012 17:59:55 +0200, Aditya Mahajan <adityam@umich.edu> wrote:

> 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.

- it may be achieved by Lua, when the table has been defined as a Lua variable:

----
\startluacode
   tab = { { "a", "b", },
           { "c", "d", },
           { "e", "f", },
           { "g", "h", },
         }
\stopluacode

\starttext
   \startluacode
     local rows1 = {}

     for i = 1, #tab, 3 do table.insert(rows1, i) end -- Define rules here - setup first set of rows

     context.setupTABLE({"row"}, rows1, {background = "color", backgroundcolor = "gray"})

     context.bTABLE()
       for i, r in ipairs(tab) do
         context.bTR()
           for j, d in ipairs(r) do
             context.bTD()
               context(d)
             context.eTD()
           end
         context.eTR()
       end
     context.eTABLE()
   \stopluacode
\stoptext
----

Best regards,

Lukas

>
> Aditya
>
> [1]: http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0001IV