NinjaScript > Language Reference > Indicator Methods >
The parabolic SAR is a technical indicator that is used by many traders to determine the direction of an asset's momentum and the point in time when this momentum has a higher-than-normal probability of switching directions.
... Courtesy of Investopedia
double; Accessing this method via an index value [int barsAgo] returns the indicator value of the referenced bar.
You can view this indicator method source code by selecting the menu Tools > Edit NinjaScript > Indicator within the NinjaTrader Control Center window.