Error on calling 'OnBarUpdate' on using Draw.Ray

[domiflichi]

Hello,

I'm super new to NinjaTrader/Script so this may be a dumb question.

Here's a snippet of my code:

protected override void OnBarUpdate()
{
Draw.Ray(this, "tag1", 10, 4808, 0, 4809, Brushes.LimeGreen); 
}

I got that line of code from https://ninjatrader.com/support/help...zontalline.htm , just slightly modified it so that it would be visible on my chart (current price is around 4813).

The problem is that when I add this to my chart (a 5M MES MAR24), it displays nothing. And in the Control Center Log, I get the following error

Indicator 'SupResIndicator': Error on calling 'OnBarUpdate' method on bar 0: You are accessing an index with a value that is invalid since it is out-of-range. I.E. accessing a series [barsAgo] with a value of 5 when there are only 4 bars on the chart.

protected override void OnBarUpdate()
{
Draw.HorizontalLine(this, "tag1", 4808, Brushes.Green);
}

I have no idea why this isn't working. Hopefully someone can point out what I'm doing wrong...

Thank you,
Jamie

[NinjaTrader_Emily]

Hello domiflichi,

Thank you for your post.

This is not a dumb question; it is a good question to help you see what your scripts are doing and get a deeper understanding of NinjaScript in general. I see in your Draw.Ray() method, you are seeing the startBarsAgo value to 10. The error is happening because when you apply a script to a chart, it runs historically on all bars of the chart. This means that when it starts on the very first bar, there are not 10 bars on the chart yet to draw a ray starting 10 bars ago and it throws the error. The following page shows how to add a check to make sure there are enough bars on the chart before taking an action, such as checking that there are at least 10 bars on the chart before drawing the ray:

https://ninjatrader.com/support/helpGuides/nt8/make_sure_you_have_enough_bars.htm

Please let us know if we may be of further assistance.

[domiflichi]

Thank you Emily, that helped!