Hello , here is mine :

// Griffiths Predictor Indicator by John F. Ehler
// Adapté pour ProRealTime
// Paramètres utilisateur
Length =18
BarsFwd =2
UpperBound =40
LowerBound =18

// Initialisation des coefficients
Coef1 = 0
Coef2 = 0
Coef3 = 0
Coef4 = 0
Coef5 = 0
Coef6 = 0
Coef7 = 0
Coef8 = 0
Coef9 = 0
Coef10 = 0
Coef11 = 0
Coef12 = 0
Coef13 = 0
Coef14 = 0
Coef15 = 0
Coef16 = 0
Coef17 = 0
Coef18 = 0

// Filtre passe-haut (High-Pass Filter)
HPPeriod = UpperBound
a1HP = EXP(-1.414 * 3.14159 / HPPeriod)
b1HP = 2 * a1HP * COS(1.414 * 180 / HPPeriod)
c2HP = b1HP
c3HP = -(a1HP * a1HP)
c1HP = (1 + c2HP – c3HP) / 4

IF BARINDEX > 2 THEN
HPPrice = (OPEN + CLOSE) / 2
HighPass = c1HP * (HPPrice – 2 * (OPEN[1] + CLOSE[1]) / 2 + (OPEN[2] + CLOSE[2]) / 2) + c2HP * HighPass[1] + c3HP * HighPass[2]
ELSE
HighPass = 0
ENDIF

// Super Smoother Filter
SSPeriod = LowerBound
a1SS = EXP(-1.414 * 3.14159 / SSPeriod)
b1SS = 2 * a1SS * COS(1.414 * 180 / SSPeriod)
c2SS = b1SS
c3SS = -(a1SS * a1SS)
c1SS = 1 – c2SS – c3SS

IF BARINDEX > 2 THEN
SuperSmoother = c1SS * (HighPass + HighPass[1]) / 2 + c2SS * SuperSmoother[1] + c3SS * SuperSmoother[2]
ELSE
SuperSmoother = 0
ENDIF

// Signal
LP = SuperSmoother
IF BARINDEX > 1 THEN
Peak = 0.991 * Peak
ENDIF
IF ABS(LP) > Peak THEN
Peak = ABS(LP)
ENDIF
IF Peak <> 0 THEN
Signal = LP / Peak
ELSE
Signal = 0
ENDIF

// Calcul de XBar
Mu = 1 / Length
XBar = Signal[0] * Coef1 + Signal[1] * Coef2 + Signal[2] * Coef3 + Signal[3] * Coef4 + Signal[4] * Coef5 +Signal[5] * Coef6 + Signal[6] * Coef7 + Signal[7] * Coef8 + Signal[8] * Coef9 + Signal[9] * Coef10 +Signal[10] * Coef11 + Signal[11] * Coef12 + Signal[12] * Coef13 + Signal[13] * Coef14 + Signal[14] * Coef15 +Signal[15] * Coef16 + Signal[16] * Coef17 + Signal[17] * Coef18

// Mise à jour des coefficients
Coef1 = Coef1 + Mu * (Signal – XBar) * Signal[0]
Coef2 = Coef2 + Mu * (Signal – XBar) * Signal[1]
Coef3 = Coef3 + Mu * (Signal – XBar) * Signal[2]
Coef4 = Coef4 + Mu * (Signal – XBar) * Signal[3]
Coef5 = Coef5 + Mu * (Signal – XBar) * Signal[4]
Coef6 = Coef6 + Mu * (Signal – XBar) * Signal[5]
Coef7 = Coef7 + Mu * (Signal – XBar) * Signal[6]
Coef8 = Coef8 + Mu * (Signal – XBar) * Signal[7]
Coef9 = Coef9 + Mu * (Signal – XBar) * Signal[8]
Coef10 = Coef10 + Mu * (Signal – XBar) * Signal[9]
Coef11 = Coef11 + Mu * (Signal – XBar) * Signal[10]
Coef12 = Coef12 + Mu * (Signal – XBar) * Signal[11]
Coef13 = Coef13 + Mu * (Signal – XBar) * Signal[12]
Coef14 = Coef14 + Mu * (Signal – XBar) * Signal[13]
Coef15 = Coef15 + Mu * (Signal – XBar) * Signal[14]
Coef16 = Coef16 + Mu * (Signal – XBar) * Signal[15]
Coef17 = Coef17 + Mu * (Signal – XBar) * Signal[16]
Coef18 = Coef18 + Mu * (Signal – XBar) * Signal[17]

// Prédiction avec BarsFwd
XPred = 0
FOR Advance = 1 TO BarsFwd DO
ProjectedSignal = Signal[Advance]
XPred = ProjectedSignal * Coef1 + Signal[Advance + 1] * Coef2 + Signal[Advance + 2] * Coef3 +Signal[Advance + 3] * Coef4 + Signal[Advance + 4] * Coef5 + Signal[Advance + 5] * Coef6 +Signal[Advance + 6] * Coef7 + Signal[Advance + 7] * Coef8 + Signal[Advance + 8] * Coef9 +Signal[Advance + 9] * Coef10 + Signal[Advance + 10] * Coef11 + Signal[Advance + 11] * Coef12 +Signal[Advance + 12] * Coef13 + Signal[Advance + 13] * Coef14 + Signal[Advance + 14] * Coef15 +Signal[Advance + 15] * Coef16 + Signal[Advance + 16] * Coef17 + Signal[Advance + 17] * Coef18
NEXT

// Retour des résultats
RETURN Signal COLOURED(0, 0, 255) AS “Signal”, XPred COLOURED(255, 0, 0) AS “XPred”

this one works :

Length= 18
BarsFwd= 2
UpperBound= 40
LowerBound= 18

REM arrays
For count= 0 TO Length+1 Do
$Coef[count]= 1/Length
NEXT

REM 2-Pole roofing filter
HPPrice= (open+close)/2
HPPeriod= UpperBound
a1= Exp(-1.414*3.14159/HPPeriod)
b1= 2*a1*Cos(1.414*180/HPPeriod)
c2= b1
c3= -a1*a1
c1= (1+ c2-c3)/4
IF 4 <= barindex THEN
$HighPass[barindex]= c1*(HPPrice – 2*HPPrice[1] + HPPrice[2]) + c2*$HighPass[barindex-1] + c3*$HighPass[barindex-2]
ELSE
$HighPass[barindex]= 0
ENDIF

SSPrice= $HighPass[barindex]
SSPeriod= LowerBound
a1= Exp(-1.414*3.14159/SSPeriod)
b1= 2*a1*Cos(1.414*180/SSPeriod)
c2= b1
c3= -a1*a1
c1= 1-c2-c3
IF 4 <= barindex THEN
$SuperSmoother[barindex]= c1*(SSPrice + SSPrice[1])/2 + c2*$SuperSmoother[barindex-1] + c3*$SuperSmoother[barindex-2]
ELSE
$SuperSmoother[barindex]= 0
ENDIF
LP= $SuperSmoother[barindex]

REM common function
Mu = 1/Length
IF 1<barindex THEN
Peak= 0.991 * Peak[1]
ELSE
Peak= 0.1
ENDIF
IF Peak < Abs(LP) THEN
Peak= Abs(LP)
ENDIF
IF Peak <> 0 THEN
Signal= LP/Peak
ENDIF
REM Perfect cycle test signal
//Signal = Sin(360*barindex / 30)

FOR Count= 1 TO Length DO
$XX[count]= Signal[Length-count]
NEXT
XBar= 0
FOR Count= 1 TO Length DO
XBar= XBar + $XX[Length-count] * $Coef[count]
Next
FOR count= 1 TO Length DO
$coef[count]= $coef[count] + Mu*($XX[Length]-XBar) *$XX[Length-count]
NEXT

REM Prediction
FOR Advance= 1 TO BarsFwd DO
XPred= 0
FOR count= 1 TO Length DO
XPred = XPred + $XX[Length+1-count] * $coef[count]
NEXT
FOR count= advance TO Length-advance DO
$XX[count]= $XX[count+1]
NEXT
FOR count= 1 TO Length-1 DO
$XX[count]= $XX[count+1]
NEXT
$XX[Length]= XPred
NEXT

Return signal coloured(0,0,250) as “Signal”, XPred coloured(250,0,0) as “xPred”, XBar[17] as “xBar”, $coef[17] coloured(0,150,0) as “Coef”