Trend Line Indicator Coding

I am trying to build a trendline indicator rather than use the drawing tool but find the example in the manual difficult to understand. It should be relatively simple to input two dates and draw a trendline between the two dates but I can't seem to get my mind around the logic shown in the help manual. Anyone able to give me some guidance?

The following is my code:

[author=RODCAM; target=price]

sdate:= InputDate("Start Date", date(2007,6,30);

cdate:= sdate;

edate:= InputDate("End Date", date(2008,1,30);

xdate:= edate;

expr:= expression("Expression",C);

period:= sdate=cdate and edate=xdate;

[name=Trend; color=blue; width=2]

trendline(expr,period,1,0,0)

maximo, thanks that is getting pretty close to the mark on what I wanted and also gives me some 'ideas' on how to approach the other coding exercise. If/when I sort out the other coding approach I'll post the results. Cheers RODCAM

I was speaking to a reliable source (who helped me with the step indicator coding to which you also responded ) today who confirmed as much. I was thinking of trying Amibroker but the coding frightened me given BS is relatively simple. Not sure if you have seen the metastocktools.com site which has some excellent coding examples for MS which may be able to be converted to BS (given the coding similarities), but on the surface they are beyond my current capability. This is an example using linear regression channel:

{ End date point }

end:=Year()>EnYear

 OR (Year()=EnYear AND (Month()>EnMnth

 OR Month()=EnMnth AND DayOfMonth()>=EnDay));

end:=end AND Alert(end=0,2);

end:=If(LastValue(Cum(Ref(end,pds)))=0,

 LastValue(Cum(1))=Cum(1),end);

{ Linear Regression Trend/Slope end-points }

lastValLRI:=LastValue(Highest(

 If(end,LinearReg(x,pds),0)));

lastValLRS:=LastValue(Highest(

 If(end,LinRegSlope(x,pds),-10000)));

adjust:=LastValue(LastValue(Cum(1))

 -Highest(If(end,Cum(1),0)));

countback:=LastValue(Cum(1))-Cum(1)-adjust;

{ Rem next line to extend plot to end of chart }

countback:=Ref(Ref(countback,-adjust),adjust);

{ Lin Reg Trendline }

LR:=lastValLRI-lastValLRS*countback;

restrict:=adjust-(LastValue(Cum(1))-pds);

LRT:=Ref(Ref(LR,-restrict),restrict);

{ Lin Reg StdDev/StdError channels }

bandType:=If(multi>=0,Stdev(x,pds),STE(x,pds));

diff:=ValueWhen(1,Cum(IsDefined(LRT))=1,

 bandType*Abs(multi));

upLR:=LRT+diff;

lwLR:=LRT-diff;

{ Plot on price chart }

upLR;lwLR;LRT

Cheers Rod

Okay another indicator finished.  Does trendlines now, above and below, support or resistance, depending on the trend. Have fun!

[target=Price; lineStyle=Solid; color=orange]

tp:=Input("Length",100,2);

os:=Input("Offset",0,0);

n := input("Width:5=Tight 10=Medium 20=Loose",10,0);

Select:=input("Channel=0 Trendline=1",0,0,1);

Regline:=Ref((LastValue(Ref(LinearReg(C,tp),-os))-

(LastValue(Ref(LinRegSlope(C,tp),-os))*

(LastValue(Ref(sum(1),-os))-Ref(sum(1),-os))))+

Ref(C,(0-(LastValue(Ref(sum(1),-os))-tp+os)))-

Ref(C,(0-(LastValue(Ref(sum(1),-os))-tp+os))),os);

Width:=HHV(H,n)-LLV(L,n);

lastpoint:=LastValue(Ref(Regline,-os));

startpoint:=LastValue(Ref(Regline,-(tp-1)-os));

CW:=valuewhen(1,Regline,lastvalue(Ref(HHV(Width*0.5,tp),-os)));

UP:=if(lastpoint > startpoint,1,0);

if(select=0,Regline-CW,if(UP=1,Regline-CW,undefined));

if(select=0,Regline+CW,if(UP=0,Regline+CW,undefined));