Whilst recently looking around for poorly written MetaStock code to use as an example for demonstrating the KISS principle (an acronym for "Keep It Simple, Stupid"), I came across this gem:

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{Restricted Display}
{Written by Preston Umrysh}
{Displays an indicator for a specified period of time}
pds:=Input("MA Lookback Periods ",2,100,10);
A:=Mov(C,pds,S);{Your Indicator Here}
len:=Input("TotalDisplayPeriods ",8,100,10);
Barbk:=Input("Right Setback",0,100,0);
len:=len+Barbk;{resets display to setback}
Signal:=Ref(A,-len);
Signal2:=Ref(A,-Barbk);
LastBar:=Cum(1)=LastValue(Cum(1)-(len));
bacdis1:=ValueWhen(1,LastBar,LastValue(Signal));
1stRefPnt:=Ref(Ref(bacdis1,-Barbk),Barbk);{end}
bacdis2:=ValueWhen(1,LastBar,LastValue(Signal2));
2ndRefPnt:=Ref(Ref(bacdis2,-Barbk),Barbk);{end}
{Line Plot }
D1:=LastValue(Cum(1))-LastValue(LEN);
{D1 is first high of line}
D2:=LastValue(Cum(1))-LastValue(BARBK);
{D2 is last high of line}
P1:=1stRefPnt; {start-of-line data array}
P2:=2ndRefPnt; {end-of-line data array}
V1:=ValueWhen(1,D1,P1);
V2:=ValueWhen(1,D2,P2);
B1:=LastValue(Cum(1))-D1;
B2:=LastValue(Cum(1))-D2;
LINE:=V1-(BarsSince(Cum(1)=D1)*( (V1-V2)/(B1-B2)));
If(LINE,A,line) {end}

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Apart from the fact that the "author" doesn't seem to understand the MetaStock code he has plagiarized, the (mostly redundant) 18 lines of plot-restriction code above can be condensed into 3 simpler lines:

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{ Bar-based plot display restriction v1.0
http://www.metastocktools.com }

{ User inputs }
pds:=Input("Indicator periods ",1,1000,10);
totPds:=Input("Total display periods",1,1000,10);
backPds:=Input("Right setback periods",0,1000,0);

{ Indicator example }
x:=Mov(C,pds,S);

{ Plot restriction }
start:=Cum(1)=LastValue(Cum(1))-totPds-backPds;
rightClip:=Ref(Ref(x,-backPds),backPds);
restricted:=rightClip*ValueWhen(1,start,1);

{ Output }
restricted

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Not only is this formula much shorter, but its logic makes some sense.

KISS - the easiest way to become proficient at writing reasonable MetaStock code.


jose '-)

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MetaStockTools.com