Below is a relatively new type of Exponential Moving Average (EMA), based on price and modulated by price peaks/troughs.

Basically, the Pivotal EMA (PEMA) generally hugs the price closer as it approaches market turning points. This can be useful as a possible improvement to the standard EMA in crossover stops.

The first PEMA version uses the standard PREV functions to construct the EMA. The second plots much faster thanks to the use of variable-period DLLs. 
MetaStock -> Tools -> Indicator Builder -> New ->
Copy and paste complete formulae between "---8<---" lines.


=============
EMA - pivotal
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{ Pivotal Exponential Moving Average v1.0 }

{ PEMA based on trough/peak support/resistance.
  Options:
   [1] Composite EMA: (Upper+Lower)/2;
   [2] Upper EMA band based on peaks;
       Lower EMA band based on troughs;
   [3] EMA shifts to Upper/Lower on crossovers }

{ ©Copyright 2004~2005 Jose Silva.
  The grant of this license is for personal use
   only - no resale or repackaging allowed.
  All code remains the property of Jose Silva.
  http://www.metastocktools.com }

{ User inputs }
pds:=Input("EMA periods",1,2520,21)/2;
plot:=Input("EMA: [1]Composite,  [2]Upper+Lower,  [3]Long/Short",1,3,1);
spread:=Input("Upper/Lower EMA bands shift %",
 0,100,2)/200;
x:=Input("use:  [1]Close,  [2]High/Low",1,2,1);

{ Peak/Troughs }
xpk:=If(x=1,C,H);
pk:=xpk<Ref(xpk,-1) AND Ref(xpk,-1)>Ref(xpk,-2);
pkVal:=ValueWhen(1,pk,Ref(xpk,-1));
xtr:=If(x=1,C,L);
tr:=xtr>Ref(xtr,-1) AND Ref(xtr,-1)<Ref(xtr,-2);
trVal:=ValueWhen(1,tr,Ref(xtr,-1));

{ Peak-based EMA }
pkpds:=If(pds>Cum(pk),Cum(pk),pds);
pkpds:=If(pkpds<1,1,pkpds);
pkEma:=pkVal*2/(pkpds+1)+PREV*(1-2/(pkpds+1));
pkEma:=pkEma*(1+spread);

{ Trough-based EMA }
trpds:=If(pds>Cum(tr),Cum(tr),pds);
trpds:=If(trpds<1,1,trpds);
trEma:=trVal*2/(trpds+1)+PREV*(1-2/(trpds+1));
trEma:=trEma*(1-spread);

{ Composite EMA }
Ema:=(pkEma+trEma)/2;
LngShtEma:=If(C>=Ema,trEma,pkEma);

{ Plot on price chart }
If(plot=1,Ema,If(plot=2,trEma,LngShtEma));
If(plot=1,Ema,If(plot=2,pkEma,LngShtEma))

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