Counting number of times an atom occurs in a table in J language

Question

In J, to count the number of times an element occurs in a list in J is:

count =: 4 : '+/x=y'"0 1. 

Alternatively, one can use the "member of interval" E. What is the equivalent expression, in J, for counting the number of times an "atom" occurs in a table?

I am also curious why the rank of "count" is given as 1 0 1, when it is specifically defined as a dyad. Why is the monad rank 1 also included? Can "count", as defined above be used as a monad?

Answer 1

I think what you are looking for is to make the table into a list using (Ravel) monadic ','and then proceed as before. So count becomes:

count=: +/@: (= ,) NB. tacit
count=: 4 : '+/ x = ,y'  NB. explicit

Cheers, bob