# avg, avgs, mavg, wavg

Arithmetic mean

## avg

Syntax: avg x, avg[x]

Where x is a numeric list, returns its arithmetic mean.

The mean of an atom is itself. Null is returned if x is empty, or contains both positive and negative infinity. Any null items in x are ignored.

q)avg 1 2 3
2f
q)avg 1 0n 2 3       / null values are ignored
2f
q)avg 1.0 0w
0w
q)avg -0w 0w
0n
q)show select ap:avg price by sym from trade
sym| ap
---| -----
a  | 10.75


avg is an aggregate function.

## avgs

Syntax: avgs x, avgs[x]

Where x is a numeric 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.

## mavg

Moving average

Syntax: x mavg y, mavg[x;y]

Where

• x is a positive int atom (not infinite)
• y is a numeric list

returns the x-item simple moving averages of y, with any nulls after the first item replaced by zero. The first x items of the result are the averages of the terms so far, and thereafter the result is the moving average. The result is floating point.

q)2 mavg 1 2 3 5 7 10
1 1.5 2.5 4 6 8.5
q)5 mavg 1 2 3 5 7 10
1 1.5 2 2.75 3.6 5.4
q)5 mavg 0N 2 0N 5 7 0N    / nulls after the first are replaced by 0
0n 2 2 3.5 4.666667 4.666667


mavg is a uniform function.

## wavg

Weighted average

Syntax: x wavg y, wavg[x;y]

Where

• x is a numeric list
• y is a numeric list

returns the average of numeric list y weighted by numeric list x. The result is a float atom. The calculation is (sum x*y) % sum x.

q)2 3 4 wavg 1 2 4
2.666667
q)2 0N 4 5 wavg 1 2 0N 8  / nulls in either argument ignored
6f


### Volume-weighted average price

The financial analytic known as VWAP is a weighted average.

q)select size wavg price by sym from trade
sym| price
---| -----
a  | 10.75


wavg is an aggregate function.

Wikipedia:Weighted average
Basics: Mathematics

## Aggregating nulls

avg, min, max and sum are special: they ignore nulls, in order to be similar to SQL92. But for nested x these functions preserve the nulls.

q)avg (1 2;0N 4)
0n 3