How to make a variable persistent

[Taddypole]

I’m trying to create an indicator that calculates a dynamic upper and lower band which should move with price.

I set an initial value of the UpperBand and LowerBand and do a check to see if that value is breached. The problem I’m having is that as soon as a bar is completed, the initial values for UpperBand and LowerBand go to zero. How do I make these values retain their previous value?

The chart I’ve attached shows a 30 sec bar chart. The horizontal lines show the UpperBand and LowerBand. If you run the code, you'll see that the values go to zero.

Anyone know how I can solve this?

Thanks,
Taddypole…

[NinjaTrader_RyanM]

Hi Taddypole,

You may want to use double here instead of DataSeries for some of these values. DataSeries store a value for every bar, so are most useful when you want index past values or use as input for an indicator. You are not doing that here, so I replaced DataSeries with doubles and ran for a few minutes -- never saw Upperband and LowerBand hit value of zero with this attached version.

[Taddypole]

Thanks Ryan,

That did the trick. Can you explain why dataseries values are not persistent?

[NinjaTrader_RyanM]

It's a different structure -- you need to set it for every bar. A double value will keep the last value you assigned to it.

[j2496i]

TaddyPole - just to clarify further, if you are interested...

A DataSeries is a type of Array... this means it can store many values, *all of which remain persistent*, until they are deleted, modified, or the array reaches it's maximum size. Generally in c# .NET, an array has a maximum size of 2GB.

An array stores it's values like this: [first value] [1] [2] [3] [4] [5] [6] [7] [next index]... [last value]

You can reference any value in an array via it's index, like this: myArray[0] (this will access the first value)

A NinjaTrader DataSeries is a 'First In First Out (FIFO)' array, meaning that the latest value will have the index [0] and the oldest value will have the index [size-1]...

You can read more here: http://msdn.microsoft.com/en-us/libr...(v=vs.71).aspx

If using more than one Bar Period, or Period Type for your charts / indicators, you need to be aware that NinjaTrader DataSeries can also be synchronized with specific members of BarsArray[], though this is beyone the scope of this post.

Hopefully that's of some help.

PS - simply put, to set the 'latest' value in the array, use:

myArray.Set( myValue );

To retrieve the latest value, and assign it to a variable, use something along the lines of:

myVariable = myArray[ 0 ];

J