BarsAgo synchronization question

[ETFVoyageur]

How does BarsAgo work when some sequences are a different length?
For example, I have Microsoft weekly and SPY weekly and I want to take the ratio: Value[0] = Close[0] / SPY[0];

I figured out that I had to skip the first bars. MSFT has 1546 bars and SPY has 1482. I would think that they'd both be accessible after skipping the first 64 bars. However, if I skip bars 0-92 I get

Error on calling 'OnBarUpdate' method on bar 93: 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.

It works fine if I skip bars 0-93. Clearly, I do not understand the bars synchronization. Why do I have to skip so many bars?

[NinjaTrader_Jesse]

Hello ETFVoyageur,

I see that you deleted your comment and said the post became obsolete, do you mean the entire thread or just the post you deleted? If this thread is obsolete I will close the case.

[ETFVoyageur]

No ... just that post.

My question about bar synchronization remains. My knowledge is evidently incomplete or incorrect so please help with the correct information:

• The situation is that I am processing two bar series that are not the same length.
• The question is how many bars OnBarUpdate() must skip before accessing both series.
• I would have thought skipping the difference in the two series' lengths but experience has proven that is wrong.
• Question: how do I calculate the number of bars for OnBarUpdate() to skip before it can access both series with [0]?
• Question: does it matter whether the longer series is the primary series?
• Question: once both series can be accessed, I presume synchronization means that [0] refers to the same bar for each -- is that correct?

[NinjaTrader_Jesse]

Hello ETFVoyageur,

When you request data that is processed based on the bars type you selected. For example if you used 5 minutes you would have 5 minute bars where data is available for each instrument. If one of the series doesn't have data for certain periods OnBarUpdate won't be called for that bars in progress during that time. The easiest way to explore this would be to use prints and print out the bar time and BarsInProgress. That will let you see which datapoints are being processed for each series.

Question: how do I calculate the number of bars for OnBarUpdate() to skip before it can access both series with [0]?

If you require 0 bars ago you dont have to calculate anything, just use 0 bars ago. If you use 1 bars ago you would use a if(CurrentBar < 1) return; condition to wait 1 bar. For multi series scripts you may also have if(CurrentBars[0] < 1 || CurrentBars[1] < 1) if you need 1 bar on each series before processing.

Question: does it matter whether the longer series is the primary series?

No

Question: once both series can be accessed, I presume synchronization means that [0] refers to the same bar for each -- is that correct?

[0] bars ago is only relevant to the series being processed. The two series are not in direct sync because they are two different instruments with different data. [0] bars ago is relevant to right now in processing on that bars in progress.

[ETFVoyageur]

[edit] I reported a problem with the indicator refreshing extremely slowly after I fixed OnBarUpdate(). I subsequently found the fix -- restart NinjaTrader. This is not the first time. I have learned that when I encounter inexplicable behavior, one thing to try is to restart NT -- that often fixes the problem.

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That aside, thanks, Jesse, your answer put me on the right track and it works fine now (since restarting NT).