"Min. Bars required" really confuses me

[pstrusi]

Hi,

Since I bought NT I began to do my back testing to several indicators and after long time wasted I realized that the parameter "Min. bar required" really changes results significantly. I've tried to read all about it in the Help guide and I think I got its concept but whenever I have to do a "realistic back testing" I really lose it.

I give you an example in order to understand this well and running real back testing, let's say that I'd like a simple strategy with a MACD, where I set this number to evaluate:

fast: from 10 to 30
slow: from 30 to 60
Smooth: from 10 to 100

Imagine that I'd like to optimize signals from that indicator, when I go to optimize tab, what will be the best realistic number to put in "Min bar required" field? 10? 100?

Thanks in advance

[NinjaTrader_Bertrand]

pstrusi, I would suggest to check out your charts with the largest MACD parameter seting you wish to use and see how many bars you need to see normalized values displayed.

[pstrusi]

But if you don't mind: could you tell me what will you do in a logic way for the earlier example, will you set in 10, 100? in order to complete the optimization

Bertrand, I'm sorry but I don't get it because what confuses me is any change in "min. bar required" changes results completely, then I wonder what is the logic and just parameter when you're optimizing, cause what anybody wants is to have a reliable system when it's in real time.

Don't worry if u don't have the answer now, I could wait if it's needed.

thanks again

[NinjaTrader_Bertrand]

Sure, it would change your results - it will tell the strategy for wait for that amout of bars counted from the series / chart start until it's firing the OnBarUpdate() calcs - if you compare calculations that need 5 bars to return meaningful values with ones that require 100 >> this setting is important : hence there's no generalized answer, you will need to be mindful what your indicator logic requires here.

[pstrusi]

Thanks Bertrand, I think I got it...so I whenever I have to do a test with several parameters-set, I will always have to fill the max number in the "min. bar required" so it can test my strategy from the lower level band till higher one, it's that correct? I mean if I have one parameter to evaluate from 1 till 100, I should put in the "min. bar required" at least 100 in order to have a good test?

Thanks

[NinjaTrader_Bertrand]

That's right, in your situation rather put in a higher # and load a more historical data then the other way around. If you're really concerned about the influence of this setting for your custom strategy, then you could also do multiple runs with different min bars required set to see which you deem best.