Package descriptive, working with frequency lists

To avoid a Maxima misfeature, the variable p needs to be declared local. Without the local declaration,
Maxima checks if p is a global array before it checks if p is a locally defined list.

frequ_mean(x) := block([sum:0, total:0],
local(p),
for p in x do
  (sum: sum+p[1]*p[2],
   total: total+p[2]),
sum/total)$

Without local(p):

(%i2) p[1,2] : 9$
(%i3) frequ_mean([[1,2],[10,20]]);
evaluation: array p must have 2 indices; found: p[1]

--Barton
________________________________