Try this formula from the library. It is based on some of JM Hurst's work. He's written some good books on this subject - check out "Profit from transaction timing" ~ that's not the exact title but something along those lines.
Plot( Close, "Price", colorWhite, styleCandle );
//------------------------------------------------------
// -------------------- HURST DE ---------------------
// --- by Ace
//------------------------------------------------------
// Hurst DE based on Centered SMA's with a forward projected
// curve based on A parabolic fit
//------------------------------------------------------
// SET THE S/T and I/T PERIODS
periodicity=Interval();
p1=Param("1) S/T DE Period",20,3,373,1);
p2=Param("2) I/T DE Period",50,3,373,1);
p3=Param("3) L/T DE Period",144,3,373,1);
//------------------------------------------------------
// Moving Averages and Lags
//------------------------------------------------------
p0=p1/2;
IIf(p1/2!=round(p1/2),p0=p0-1,p0=p0);
Ave0=MA(Avg,p0);
Ave1=MA(Avg,p1);
Ave2=MA(Avg,p2);
Ave3=MA(Avg,p3);
Lag0=(p0+1)/2;
Lag1=(p1+1)/2;
Lag2=(p2+1)/2;
Lag3=(p3+1)/2;
//------------------------------------------------------
// Center the MA's
//------------------------------------------------------
cma0=Ref(Ave0,Lag0);
cma1=Ref(Ave1,Lag1);
cma2=Ref(Ave2,Lag2);
cma3=Ref(Ave3,Lag3);
//------------------------------------------------------
// Percentage Based Widths
//------------------------------------------------------
k=3;
dp1=LastValue(Ref(StDev( (Close-cma1)/cma1, k*p1 ),(p1+1)/2-1));
dp2=LastValue(Ref(StDev( (Close-cma2)/cma2, k*p2 ),(p2+1)/2-1));
dp3=LastValue(Ref(StDev( (Close-cma3)/cma3, k*p3 ),(p3+1)/2-1));
//------------------------------------------------------
// Arithmetic Widths
//------------------------------------------------------
/*
Hilo=IIf(H-cma1>=cma1-L,H-cma1,L-cma1);
//dp1=LastValue(Ref(StDev( (Close-cma1), k*p1 ),-Lag1));
dp1=LastValue(Ref(StDev( Hilo, k*p1 ),-Lag1));
Hilo=IIf(H-cma2>=cma2-L,H-cma2,L-cma2);
//dp2=LastValue(Ref(StDev( Close-cma2, k*p2 ),-Lag2));
dp2=LastValue(Ref(StDev( Hilo, k*p2 ),-Lag2));
Hilo=IIf(H-cma3>=cma3-L,H-cma3,L-cma3);
//dp3=LastValue(Ref(StDev( Close-cma3, k*p3 ),-Lag3));
dp3=LastValue(Ref(StDev( Hilo, k*p3 ),-Lag3));
*/
//------------------------------------------------------
// Calculate a Parabolic Extension for the S/T DE
//------------------------------------------------------
tn=round(p1/6);
fillforward=BarIndex() >= LastValue( BarIndex() )-Lag1;
t=BarIndex()-Ref(BarIndex(),Lag1)+Lag1;
// Get Constants for the Parabolic fit equation
Sm=LastValue(Ref(Ave1,-2*tn));
// This coordinate is actually t=0
So=LastValue(Ref(Ave1,-tn));
Sp=LastValue(Ave1);
// Calculate coeff's for the parabola
Ak=So;
Bk=(Sp-Sm)/2/tn;
Ck=(Sp+Sm-2*So)/2/tn^2;
parabfit1=Ak+Bk*t+Ck*t^2;
dy1=LastValue(Ave1)-Ak;
cma1=IIf(fillforward,parabfit1+dy1,cma1);
//------------------------------------------------------
// Calculate a Parabolic Extension for the I/T DE
//------------------------------------------------------
tn=round(p2/6);
fillforward=BarIndex() >= LastValue( BarIndex() )-Lag2;
t=BarIndex()-Ref(BarIndex(),Lag2)+Lag2;
// Get Constants for the Parabolic fit equation
Sm=LastValue(Ref(Ave2,-2*tn));
// This coordinate is actually t=0
So=LastValue(Ref(Ave2,-tn));
Sp=LastValue(Ave2);
// Calculate coeff's for the parabola
Ak=So;
Bk=(Sp-Sm)/2/tn;
Ck=(Sp+Sm-2*So)/2/tn^2;
parabfit2=Ak+Bk*t+Ck*t^2;
dy2=LastValue(Ave2)-Ak;
cma2=IIf(fillforward,parabfit2+dy2,cma2);
//------------------------------------------------------
// Calculate a Parabolic Extension for the L/T DE
//------------------------------------------------------
tn=round(p3/6);
fillforward=BarIndex() >= LastValue( BarIndex() )-Lag3;
t=BarIndex()-Ref(BarIndex(),Lag3)+Lag3;
// Get Constants for the Parabolic fit equation
Sm=LastValue(Ref(Ave3,-2*tn));
// This coordinate is actually t=0
So=LastValue(Ref(Ave3,-tn));
Sp=LastValue(Ave3);
// Calculate coeff's for the parabola
Ak=So;
Bk=(Sp-Sm)/2/tn;
Ck=(Sp+Sm-2*So)/2/tn^2;
parabfit3=Ak+Bk*t+Ck*t^2;
dy3=LastValue(Ave3)-Ak;
cma3=IIf(fillforward,parabfit3+dy3,cma3);
//------------------------------------------------------
// Fast MA with parabolic fit - p1/2 period
//------------------------------------------------------
tn=round(p0/6);
fillforward=BarIndex() >= LastValue( BarIndex() )-Lag0;
t=BarIndex()-Ref(BarIndex(),Lag0)+Lag0;
// Get Constants for the Parabolic fit equation
Sm=LastValue(Ref(Ave0,-2*tn));
// This coordinate is actually t=0
So=LastValue(Ref(Ave0,-tn));
Sp=LastValue(Ave0);
// Calculate coeff's for the parabola
Ak=So;
Bk=(Sp-Sm)/2/tn;
Ck=(Sp+Sm-2*So)/2/tn^2;
parabfit0=Ak+Bk*t+Ck*t^2;
dy0=LastValue(Ave0)-Ak;
cma0=IIf(fillforward,parabfit0+dy0,cma0);
//------------------------------------------------------
Plot( Close, "OHLC", colorBlack, styleCandle);
//------------------------------------------------------
// Plot Arithmetic Bands
//------------------------------------------------------
/*
//Plot(cma1,"I/T-CTR",colorRed,styleLine);
Plot(cma1+2*dp1,"S/T-UB",colorRed,styleLine);
Plot(cma1-2*dp1,"S/T-LB",colorRed,styleLine);
//Plot(cma2,"I/T-CTR",colorBlue,styleLine);
Plot(cma2+2*dp2,"I/T-UB",colorBlue,styleLine);
Plot(cma2-2*dp2,"I/T-LB",colorBlue,styleLine);
//Plot(cma3,"L/T-CTR",colorGreen,styleLine);
Plot(cma3+2*dp3,"L/T-UB",colorGreen,styleLine);
Plot(cma3-2*dp3,"L/T-LB",colorGreen,styleLine);
Plot(cma0,"Zline",colorBrown,styleLine);
*/
//------------------------------------------------------
// Write the selected bar lengths to the window
//------------------------------------------------------
"HURST DOMINANCY ENVELOPES";
"Current Periods are set to: ";
"S/T Period: "+WriteVal(p1,3.0);
"I/T Period: "+WriteVal(p2,3.0);
"L/T Period: "+WriteVal(p3,3.0);
" ";
"Select a range on the screen to calculate a period.";
" ";
rangelength = EndValue( BarIndex() ) - BeginValue( BarIndex() );
"Selected Range is "+
WriteVal( rangelength, format = 3.0 )+
" bars";
//------------------------------------------------------
// Use the below plotting for % Width Bands
//------------------------------------------------------
m=2.2;
Plot(cma1*(1+m*dp1),WriteVal(p1,3.0)+"p"+" UB",colorRed,styleLine);
Plot(cma1*(1-m*dp1),"LB",colorRed,styleLine);
Plot(cma2*(1+m*dp2),WriteVal(p2,3.0)+"p"+" UB",colorBlue,styleLine);
Plot(cma2*(1-m*dp2),"LB",colorBlue,styleLine);
Plot(cma3*(1+m*dp3),WriteVal(p3,3.0)+"p"+" UB",colorGreen,styleLine);
Plot(cma3*(1-m*dp3),"LB",colorGreen,styleLine);
ub=cma1*(1+m*dp1);
Lb=cma1*(1-m*dp1);
inpercentage1=Sum(IIf(H<ub AND H>lb AND L<ub AND
L>lb,1,0),3*p1)/3/p1*100;
"";
ub=cma2*(1+2*dp2);
Lb=cma2*(1-2*dp2);
inpercentage2=Sum(IIf(H<ub AND H>lb AND L<ub AND
L>lb,1,0),3*p2)/3/p2*100;
ub=cma3*(1+2*dp3);
Lb=cma3*(1-2*dp3);
inpercentage3=Sum(IIf(H<ub AND H>lb AND L<ub AND
L>lb,1,0),3*p3)/3/p3*100;
"";
WriteVal(inpercentage1,3.0)+"% prices within 1st DE over 3 Periods";
WriteVal(inpercentage2,3.0)+"% prices within 2nd DE over 3 Periods";
WriteVal(inpercentage3,3.0)+"% prices within 3rd DE over 3 Periods";
PlotShapes(IIf(Cross(BarIndex(),BarCount-1-
(p1+1)/2),shapeSmallUpTriangle,0), colorRed, 0, cma1*(1-2*dp1));
PlotShapes(IIf(Cross(BarIndex(),BarCount-1-
(p2+1)/2),shapeSmallUpTriangle,0), colorBlue, 0, cma2*(1-2*dp2));
PlotShapes(IIf(Cross(BarIndex(),BarCount-1-
(p3+1)/2),shapeSmallUpTriangle,0), colorGreen, 0, cma3*(1-2*dp3));
//------------------------------------------------------
// Clyde Lee said that Hurst recommended going back one
// full cycle to and copy that centerline shape to the
// shifted CMA to project forward for the envelopes.
//------------------------------------------------------
dy1=LastValue(Ref(cma1,-3*p1/2))-LastValue(Ref(cma1,-p1/2));
RefCMA1=IIf(BarIndex()>=BarCount-p1/2-1,Ref(cma1,-p1),Null)-dy1;
Plot(RefCMA1*(1+m*dp1),"RefUB1",colorOrange);
Plot(RefCMA1*(1-m*dp1),"RefLB1",colorOrange);
dy2=LastValue(Ref(cma2,-3*p2/2))-LastValue(Ref(cma2,-p2/2));
Refcma2=IIf(BarIndex()>=BarCount-p2/2-1,Ref(cma2,-p2),Null)-dy2;
Plot(Refcma2*(1+m*dp2),"RefUB1",colorLightBlue);
Plot(Refcma2*(1-m*dp2),"RefLB1",colorLightBlue);
dy3=LastValue(Ref(cma3,-3*p3/2))-LastValue(Ref(cma3,-p3/2));
Refcma3=IIf(BarIndex()>=BarCount-p3/2-1,Ref(cma3,-p3),Null)-dy3;
Plot(Refcma3*(1+m*dp3),"RefUB1",colorSeaGreen);
Plot(Refcma3*(1-m*dp3),"RefLB1",colorSeaGreen);
a1=(C-Ref(C,-1))/(Ref(C,-1))*100;
b = 1041231;
a=DateNum()==b;
i=ValueWhen(a,C);
ii = ((C-i)/i)*100;
Title = Name() + " - " + WriteVal( DateTime(), formatDateTime ) + " - " + " Open: " + O + ", Hi: " + H + ", Low: " + L + ", Close: " + C + " " + NumToStr(a1,1.2) + "%" + ", Volume: " + Writeb =
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Rakesh Sahgal <rakeshsahgal@xxxxxxxxx> wrote: