To answer your last question first, it looks like "1/2" means rank 1 or rank 2, e.g.
(1 0 1 0,:1 0 0 1) <;.1 i. 4 4 +---------+-----------+ |0 1 2 3 | 8 9 10 11| |4 5 6 7 |12 13 14 15| +---------+-----------+ |0 1 2 3|12 13 14 15| |4 5 6 7| | |8 9 10 11| | +---------+-----------+ applies each rank 1 element of the boolean left argument. So, the "1 0 1 0" returns the evenly divided first row of the result and the "1 0 0 1" returns the uneven division in the second result row. With integer rank 2 left arguments like this ((0 0,:2 2),:1 1,:3 3) <;.0 i. 4 4 +---+--------+ |0 1| 5 6 7| |4 5| 9 10 11| | |13 14 15| +---+--------+ it applies each rank 2 of the numeric left argument, so you get a 2x2 starting at position (0,0) for the first left-hand matrix and a 3x3 starting at position (1,1) for the second. As far as adding up rows within the partitions, here's a few ways. (1 0 1;1 0 0 1) <;.1 i. 3 4 +------+--+ |0 1 2 |3 | |4 5 6 |7 | +------+--+ |8 9 10|11| +------+--+ I changed the left argument from your example because it's more interesting to have more than one row in some of the addends. So, you can sum after partitioning: +/&.>(1 0 1;1 0 0 1) <;.1 i. 3 4 +------+--+ |4 6 8 |10| +------+--+ |8 9 10|11| +------+--+ Or without partitioning (1 0 1;1 0 0 1) +/;.1 i. 3 4 4 6 8 10 0 0 8 9 10 11 0 0 But this gives you extraneous zeros because of the padding required to equalize the rows of the unenclosed result. Lastly, you can enclose and sum at the same time: (0 1 1;1 0 0 1) ([:<+/);.1 i. 3 4 +------+--+ |4 5 6 |7 | +------+--+ |8 9 10|11| +------+--+ Hope this helps. On Sun, Oct 19, 2008 at 8:57 AM, Don Guinn <[EMAIL PROTECTED]> wrote: > Playing with J for C and got to "Apply On Specified Partitions: Dyad u;.1 > and u;.2". Replaced the < with +/ and it didn't sum the rows. After looking > at the result a little more closely I discovered that each cell contained a > table instead of a row. > (0 1 1;1 0 0 1) <;.1 i. 3 4 > +------+--+ > |4 5 6 |7 | > +------+--+ > |8 9 10|11| > +------+--+ > (0 1 1;1 0 0 1) (<@$);.1 i. 3 4 > +---+---+ > |1 3|1 1| > +---+---+ > |1 3|1 1| > +---+---+ > > I can't figure out why. > > Also, in the Dictionary for Cut it describes the rank as "_ 1/2 _". What > does the "1/2" mean? Needless to say, I still have a long way go to fully > understand Cut. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
