Go Back   NinjaTrader Support Forum > NinjaScript Educational Resources > Tips

Tips Official NinjaScript tips and tricks

Thread Tools Display Modes
Old 08-04-2009, 11:03 AM   #1
NinjaTrader Product Manager
NinjaTrader_Josh's Avatar
Join Date: May 2007
Location: Denver, CO
Posts: 17,460
Thanks: 1
Thanked 191 times in 85 posts
Default Using [] brackets

In C#, square brackets represent a way to access values stored within an array. NinjaScript comes with quite a few arrays that we call DataSeries objects which could be accessed with square brackets. DataSeries objects are linked to the underlying bars series in that they hold the same number of values as the number of bars on a chart. For example, to get the close price one bar ago, you would use Close[1] since the value of 1 within the square brackets represents the number of bars ago whose value you wish to reference. As another example, to get the high three bars ago, you would use High[3].

double close1 = Close[1]; // gets the close price one bar ago
double high3 = High[3]; // gets the high of three bars ago
double low = Low; // results in compile error. Low is an array, and can't be accessed directly. It should be Low[n Bars ago].
Many of NinjaTrader's indicators store their values in plots. Plots are essentially DataSeries objects and to retrieve values from them you need to specify which value you want to access. In most cases, you'd like the current value, so you could use SMA(14)[0], not just SMA(14). SMA(14) is the DataSeries, and you can't access it directly. Using SMA(14)[0] retrieves the part of the DataSeries you're interested in--the most current value.

double SMA_current = SMA(14)[0]; // gets the current value of the SMA
double SMA_1 = SMA(14)[1]; // gets the SMA value one bar ago
double SMA_value = SMA(14); // results in compile error. SMA(14) is a DataSeries and the variable SMA_value of type double can't hold a DataSeries.
Most of the time, you need an index value (number in the square brackets), but there are also cases when you need to use the DataSeries instead. CrossAbove() and CrossBelow() are two key examples. If you look at the reference page for CrossAbove(), the two method signatures (overloads) look like this:

CrossAbove(IDataSeries series1, double value, int lookBackPeriod)
CrossAbove(IDataSeries series1, IDataSeries series2, int lookBackPeriod)
This means the first variable must always be a DataSeries object, and the second variable can be either another DataSeries or a double value (100, 70.25, etc). To specify a DataSeries object, you can just leave off the square brackets. For example if(CrossAbove(SMA(14), SMA(28), 1)) checks if the 14 period SMA has crossed above the 28 period SMA within the last bar. if(CrossAbove(SMA(14)[0], SMA(28)[0], 1)) would give you a compile error because it expects a DataSeries as input,not a double value (which is returned when an index is present).

if (CrossAbove(SMA(14), SMA(28), 1)) // works fine
if (CrossAbove(SMA(14), 1000, 1)) // works fine, this uses a double for the second argument. See the above overload.
if (CrossAbove(SMA(14)[0], SMA(28)[0], 1)) // compile error: SMA(14)[0] is a double, not a DataSeries
if (CrossAbove(SMA(14), SMA(28)[0], 1)) // would work fine with a DataSeries as first argument and a double as the second argument
NinjaTrader_Josh is offline  
Reply With Quote
The following 2 users say thank you to NinjaTrader_Josh for this post:

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Moving your stopo and profit orders in OCO brackets sourcem SuperDOM and other Order Entry Windows 2 03-16-2009 05:40 AM
brackets mario73 ATM Strategies (Discretionary Trading) 1 02-04-2009 04:43 AM
Compiling problems- brackets and statement Mark_486 Strategy Analyzer 1 05-15-2008 01:40 AM

All times are GMT -6. The time now is 03:37 AM.

FULL RISK DISCLOSURE: Futures trading contains substantial risk and is not for every investor. An investor could potentially lose all or more than the initial investment. Risk capital is money that can be lost without jeopardizing ones financial security or lifestyle. Only risk capital should be used for trading and only those with sufficient risk capital should consider trading. Past performance is not necessarily indicative of future results. View Full Risk Disclosure.