Strange behavior when trying to move trendlines

July 31st, 2017, 01:43 AM

I am an experienced developer but new to EL.

I am using trend lines to mark horizontal price levels. What I want to do is mark local highs and lows from the bar where they originate all the way to the right edge of the chart. So I mark the level but then want to move the line up for highs or down for lows when a slightly higher high or lower low is discovered.

Code

using elsystem.drawingobjects;
using elsystem.drawing;

vars:
	TrendLine tl(null),        // reusable variable
	TrendLine mrh(null),    // reference to most recent high TL
	TrendLine mrl(null);     // reference to most recent low TL

        ...

        // create an initial price level line
	tl = TrendLine.create(BNPoint.create(BarNumber, high), bnpoint.create(99999, high));
	tl.Persist = true;
	tl.color = color.fromname("red");
	DrawingObjects.add(tl);
	mrh = tl;

I started out trying to simply move the existing line:

Code

mrh.StartPoint.Price = High;
mrh.EndPoint.Price = High;

For some reason, that does not work. Any idea why not? It seems like it should.

Plan B was to delete the existing line and create a new line at the new level:

Code

                DrawingObjects.Delete(mrh);
		tl = TrendLine.create(BNPoint.create(BarNumber, high), bnpoint.create(99999, high));
		tl.Persist = true;
		tl.Color = color.fromname("red");
		DrawingObjects.add(tl);
		mrh = tl;

This code also behaves very strangely. If I run it as is, my print statements show that it is processing the code, yet it never deletes the original line, and it never creates new lines.

However, if I comment out the line that says DrawingObjects.Delete(mrh);, then I get all the lines. (To be clear, all I want is the most extreme high and low, not all of the interim steps on the way to them.)

There must be something I do not understand about the references to these drawing objects. Is the problem that I am reusing the variables tl and mrh and mrl? Am I forced to create a new variable for each line? Or is there some other problem that I completely missing?

It almost seems like the lines are not executed in the order that they appear, as if the lines are being drawn and then instantly deleted. So with the call to Delete() commented out, the drawn lines remain.

Any insights appreciated!

ABCTG · July 31st, 2017, 09:40 AM

greymatter,

EndPoint and StartPoint are read only. Although the help states StartPoint.Price is get/set, it might be just be a mistake in the help. You can use the SetStartPoint and SetEndPoint methods of the trendline class instead to update the location.

Regards,

ABCTG

Strange behavior when trying to move trendlines

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Strange behavior when trying to move trendlines