len - lookback period
avg - smoothing average period
The Stochastic Oscillator measures the position of a value in a range of similar values, with optional smoothing.
STOC(len, avg) could also be expressed as 100 * Avg((C - Lowest(L, len)) / (Highest(H, len) - Lowest(L, len)), avg).
STOC(1,1) is therefore a simple way to calculate "Internal Bar Strength", i.e., 100*(C-L)/(H-L).
In case you're looking for the "Williams %R" indicator, that is simply -1 * (100 - STOC(len, 1)).