Average Directional Movement index (.ADX)

ADX = modify moving average of DX
DX = 100 x ( (+DI - -DI)/( +DI + -DI) )
+DI = +DMn / TRn , -DI = -DM / TRn
+DM = Ht - Ht-1 , -DM = Lt - Lt-1
CL = Ct - Ct-1
TR = largest of +DM,-DM ,and CL
where :
+DI = current positive directional index
-DI = current negative directional index
+DMn = current modified moving average of +DM
+DM = current positive directional movement value
Ht = current hign
Ht-1 = previous high
Lt = current low
Lt-1 = previous low
-DMn = current modified moving average of -DM
-DM = current negative directional movement value
TRn = current modified modified moving average of the true range
TR = true range
n = number of periods
DX = current DX
reference from : J.Welles Wilder