Running averages
avgs x avgs[x]
Where x is a numeric or temporal list,
returns the running averages, i.e. applies function avg to successive prefixes of x.
q)avgs 1 2 3 0n 4 -0w 0w
1 1.5 2 2 2.5 -0w 0n
avgs is a uniform function, equivalent to (avg\).