Is it Correct to calculate SMA like this?

[wolfcuring]

Ninja Trader has given the Algorithm of SMA like this :

if (CurrentBar == 0)
Value.Set(Input[0]);
else
{
double last = Value[1] * Math.Min(CurrentBar, Period);

if (CurrentBar >= Period)
Value.Set((last + Input[0] - Input[Period]) / Math.Min(CurrentBar, Period));

else
Value.Set((last + Input[0]) / (Math.Min(CurrentBar, Period) + 1));
}

So, for example, if the Period=14, and CurrentBar=15, SMA=(Value[1]*14+Input[0]-InPut[14])/14 . Then, instead of adding up the last 14 bars, it just simply use the Value*14 ?

It seems quite confused to me, any suggestion ?

[NinjaTrader_Bertrand]

Welcome here to our forums wolfcuring, the calculation is valid and correct, it's just a more elegant way saving processing power. If you compare the result to for example to SUM(14) / 14 >> it would be exactly the same.

[wolfcuring]

Thank you Bertrand

[wolfcuring]

Hi Bertrand,

About the coding of SMA, then I guess the Value[1] must be representing the median from on bar ago? I checked carefully the help manual, but still get a little confused, what the "Value" is and how Ninja will process the price data.

I have been through a C# tutorial and the Ninja Script reference. Any suggestion how to get further?

[NinjaTrader_Bertrand]

Hi wolfcuring, this would simply be the indicator main value series - http://www.ninjatrader.com/support/h.../nt7/value.htm

[koganam]

Hi Bertrand,

About the coding of SMA, then I guess the Value[1] must be representing the median from on bar ago? I checked carefully the help manual, but still get a little confused, what the "Value" is and how Ninja will process the price data.

I have been through a C# tutorial and the Ninja Script reference. Any suggestion how to get further?

SMA = RunningTotalValue / Period.

Therefore, SMA(PreviousBar) = RunningTotalValue(PreviousBar) / Period.
Therfefore, RunningTotalValue(PreviousBar) = SMA(PreviousBar) * Period.
Therefore, RunningTotalValue(ThisBar) = RunningTotalValue(PreviousBar) + Value(ThisBar) - Value(PeriodBarsAgo).

Finally, SMA(ThisBar) = RunningTotalValue(ThisBar) / Period.

[wolfcuring]

Thank you Koganam.

What seems to be most confusing to me is what does Value[int x] represent. The language of the user manual is not quite 'reader friendly'.

Besides, as a newbie to coding, I enjoy the simplicity and beauty of these algorithm.

[koganam]

Thank you Koganam.

What seems to be most confusing to me is what does Value[int x] represent. The language of the user manual is not quite 'reader friendly'.

Besides, as a newbie to coding, I enjoy the simplicity and beauty of these algorithm.

Value is the default first Plot. if one is not explicitly defined in the public properties.

It is indexed backwards from the CurrentBar, (CurrentBar is zero). Therefore, Value[x] where x is an integer, is the value of the Plot "x bars" ago, counting from the CurrentBar. eg., the previous bar is always Value[1], 2 bars ago is Value[2] etc.