Ninjascript Array handling

[FREEN]

I have a dataseries that is "isolated" in a if statement. When the if criterias are not met, NT still gives the dataseries a value (0).

Like this: 11,0,0,0,13,0,0,0,0...

In C# I would expect this array to look like this: 11,13...

Is an array in Ninjascript always a "bars array"?

[NinjaTrader_Bertrand]

Correct, a dataSeries is tied to the bars it's linked to - you should always set a value and then filter in your conditions as needed as otherwise exceptions accessing the series could be the result.

[NinjaTrader_RyanM1]

Hi Freen,

Yes, DataSeries are always synced to bars. There will be the same number of elements in the data series as bars.

http://www.ninjatrader.com/support/helpGuides/nt7/dataseries_class.htm

Calling the Reset() method is unique and can be very powerful for custom indicator development. DataSeries objects can hold null values which simply means that you do not want to store a value for the current bar. Mathematically, you can correctly assign a value of zero however if the DataSeries was the primary DataSeries of an indicator whose values would be used for plotting, you may NOT want a zero value plotted. Meaning, you want a zero value for proper calculations but not a zero value for chart visualization. The Reset() method allows you to reset the current bar's DataSeries value to a zero for calculation purposes but NinjaScript would ignore this value when it plotted it on a chart.

[FREEN]

Thanks Ryan and Bertrand, I´m always impressed by your promtness. And thanks for the additonal info Ryan, you answered my sequel question.

[FREEN]

Can´t find the Reset() method in the Alphabetic reference. Would you kindly point me to it´s syntax and usage?!

Tried this but I still get the zeroes:

if (highestbar<1) // ie: highestbar=0
{
HighestbarDS.Reset();
}
else
{
HighestbarDS.Set(highestbar);
}


...and NT won´t allow a "Null" setting:


if (highestbar<1)
{
HighestbarDS.Set(Null);
}
else
{
HighestbarDS.Set(highestbar);
}


Guess I´ll have to read the array in loop excluding the zeroes into a new array.

[NinjaTrader_RyanM1]

DataSeries reset is called with:

myDataSeries.Reset();

[FREEN]

DataSeries.Set(intbarsAgo, doublevalue)

You can also set the value for historical bars by including a "barsAgo" value that represents the number of bars ago that you want the double value to be stored at.

Q 1: Is the old value simply overwritten or does it have to be reset before set?

Q 2: Is the rest of the array unaffected?


//Fredrik

[FREEN]

Q 1: Is the old value simply overwritten or does it have to be reset before set?

Q 2: Is the rest of the array unaffected?


//Fredrik

Found out testing it;

A 1: Yes, it´s simply overwritten. No, it needn´t be reset before it´s overwritten!

A 2: Yes!

[FREEN]

As a conclusion and for anyone in need, here´s the snippet that filters all "barsAgo zeroes" added by NT to an array out. In my case I wanted an array of peaks instead of an "barsAgo array". Example;

input ds: 0,0,0,0,0,0,12,0,0,0,0,56,0,0,0,0,0,0,0,87,0,0,0 (HighestbarDS in the code)

output ds: 12, 56, 87 (PeaksDS in the code)

Code snippet:

int i = 0; // used in reading "HighestbarsDS" array index value
int j = 0; // used in setting "PeaksDS" custom array index value

while (i < 256) // maximum bars lookback if not set to infinite
{
if (HighestbarDS[i] != 0) // filter out all zeroes
{
PeaksDS.Set( j, (int)HighestbarDS[i]); // read from HighestbarDS[i]- set to PeaksDS[j]
j++; // incrementing only when HighestbarsDS != 0
}
i++; // incrementing for each barsAgo index value
}

[NinjaTrader_Bertrand]

Frederic, your conclusions are correct - thanks for sharing the snippet with our members here.

[FREEN]

De nada Bertrand. You guys make an excellent job and I´m happy if I can contribute with more than just newbie questions.