So, I have never used sparse arrays in J before, and am puzzled by some of the behavior. If I initialize an integer sparse vector BID, and set element 10 to be 90:
BID=: 1 $. 100;0;3-3 BID=: (90) 10}BID BID 10 │ 90 Cool; but then, if I want to zero out the 10 element BID=: (90-90) 10}BID BID 10 │ 0 Not cool; especially when I want to use 4&$. to find the nonzero elements: 4&$.BID 10 Am I expecting too much from sparse vectors? Or am I assuming something silly? FWIIW, I checked on 702 and 801; same behavior. Was trying to use sparse vectors as a sort of numeric keyed hash table. It's probably not much use doing this if the 0 valued elements return an index with 4&$. Thanks for any insights, -Scott ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
