] x=: 20 ?...@$ 7 6 2 1 2 6 5 6 1 3 0 0 4 3 3 5 1 2 5 5 5 <: #/.~ (i.7) ,x 2 3 3 3 1 5 3
This is assuming you know "the universe" that should be prefaced to x before the application of #/.~ . ----- Original Message ----- From: Zsbán Ambrus <[email protected]> Date: Sunday, September 5, 2010 12:01 Subject: [Jprogramming] Mask from list of indices with multiplicity To: [email protected] > If I have a list of indices with possible repetitions, such as > > i=: 1 3 1 > > how do I convert it to a mask m so that n{m is the number of > occurrences of n in i ? > > m=: +/ i =/ i. >: >./ i > 0 2 0 1 > > I can convert from the mask to the (sorted) list of indices with the > I. builtin, eg. > > I. m > 1 1 3 > > but is there a simpler way for the conversion to mask? > Would it make > sense if I.^:_1 did this? ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
