Showing specific number of drawings only.

[several]

Hello. I wonder if someone can help me. Assume I have an indicator that draws arrows under bars that are greater than 20 ticks.

I know I can only show the most recent arrows by keeping the tag the same in the draw.uparrow object.

I know I can show all arrows by adding CurrentBar[0] or something to the tag to make each arrow a unique name.

But what if I wanted to show only the last 4 arrows? or only the last 10 arrows. How would I achieve something like that?

[NinjaTrader_Gaby]

Hello several,

Thank you for your post.

One idea is to keep track of the drawing objects you've created by adding their tag names to a list or series so you can delete them later. Once the last is greater than 4 elements, call RemoveDrawObject on the 5th element which will contain the tag name for the 5th drawing.

https://ninjatrader.com/support/helpguides/nt8/removedrawobject.htm

[eDanny]

A simple way is to use a counter: int ArrowCtr
Include the counter in the arrow object, something like this: "MyArrow" + ArrowCtr
Have a parameter for kept arrows: int ArrowsToKeep = 4
Draw your new arrow, then remove an arrow: RemoveDrawObject("MyArrow" + (ArrowCtr - ArrowsToKeep));
Then increment your counter: ArrowCtr ++;

Edit: I see Gaby already responded too. My example will use less memory but both would work.

[several]

Thanks guys!! Will try it.

[StealthM93]

Another approach is letting the math processor do the work for you using the modulo operator.

private string const string UNIQUE_TAG_PREFIX = "myUniquePrefix"; // to avoid naming collisions
private int arrowCounter = 0;

[NinjaScriptProperty]
[Range(1, 100)]
[Display(GroupName = "Parameters", Order = 1, Name = "Number of Arrows", Description = "How many arrows to display. Max 100")]
public int NumberArrows { get; set; }

In the looping logic within OnBarUpdate()

arrowCounter = ++arrowCounter % NumberArrows;
string myRotatingTag = UNIQUE_TAG_PREFIX + arrowCounter;
// Use the myRotatingTag in the Draw method.

If you understand the modulo operator, you'll see that code will rotate through NumberArrows tags. By repeating the tags on a rotating basis, the old is automatically replaced with the new by the NT8 rendering engine.

Hope that helps!
Matt