The indicator in Williams %R is expressed quite differently from other Oscillator analysis. You have to pay attention that the momentum is presented by the figures, 0 to -100, and the forex market exceeds to buy when the momentum shows upper than -20 and it exceeds to sell when lower than -80. It is, however, basically the same as other Oscillator analysis in the point that it inquires where the recent market price is relatively located in comparison to the past few days in order to judge the market in overheating or not.
Williams %R is developed for the short term forex trading and is often used for trend protesting. Williams %R reflects more sensitive to the market movement than other Oscillator analysis, but the cheat on the chart happens most frequently.