Indicator error "outside the bounds of the array"

[Gianpiero]

I'm writing an indicator. When I apply it to a price chart, I get this error:

Error on calling 'OnBarUpdate' method on bar 44: Index was outside the bounds of the array.

Which array does it refer to? Setting:

MaximumBarsLookBack = MaximumBarsLookBack.Infinite;

in

State.SetDefaults

does not solve this issue.

Finally, I looked at bar 44 but didn't find anything wrong with it.

[NinjaTrader_BrandonH]

Hello Gianpiero,

Thanks for your post.

This means an invalid index was used somewhere in your script.

For example, with the error:

"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"

This message also indicates an invalid index was used.

As one example, calling Close[1] when CurrentBar is 0 (the very first bar) will cause this error.

The reason for this is because there will not be a bar ago; essentially there is not enough data at bar 0 look back one bar.

The script will start from the far left of the chart at the very beginning where the CurrentBar will equal 0 and then start working to the right, calling OnBarUpdate() for each bar.

In this specific example, it would be needed to wait for the second bar to be built (from all series if there are multiple series added), to ensure that you have enough data to call a index 1 bar ago.

This is especially important when multiple series are added to a single script as the data for all series may not start at the same time.

Below is a link to the help guide on this specific example of an indexing error.
https://ninjatrader.com/support/helpGuides/nt8/make_sure_you_have_enough_bars.htm

Also, below are links to the help guide on CurrentBar and CurrentBars.
https://ninjatrader.com/support/helpGuides/nt8/currentbar.htm
https://ninjatrader.com/support/helpGuides/nt8/currentbars.htm

Indexing errors can also occur when using an invalid index with arrays or collections.

Below are public links to 3rd party educational sites on arrays and index out of range errors.

https://www.dotnetperls.com/array

Ultimately, debugging prints would have to be added to your script that prints out each index you are accessing in your script along with the CurrentBar to find the exact line of code in your script causing the error. Note that CurrentBar must be greater than or equal to the index you are accessing in the script and negative indexes cannot be accessed.

Below is a link to a forum post that demonstrates how to use prints to understand behavior.
https://ninjatrader.com/support/foru...121#post791121

[Gianpiero]

Thank you but beware some links return error 404, page not found.

[QuantKey_Bruce]

Compile in debug mode, then examine the trace file in Documents -> NinjaTrader 8 -> trace -> today's date.txt to see the line number of your script that is the source of the error.

[NinjaTrader_BrandonH]

Hello Gianpiero,

Thanks for your notes.

I have updated the links in post # 2 and also shared the link below.

Below is a link to the help guide on this specific example of an indexing error.
https://ninjatrader.com/support/helpGuides/nt8/make_sure_you_have_enough_bars.htm

Also, below are links to the help guide on CurrentBar and CurrentBars.
https://ninjatrader.com/support/helpGuides/nt8/currentbar.htm
https://ninjatrader.com/support/helpGuides/nt8/currentbars.htm

[Gianpiero]

You are awesome!