<series> output = <series>.subset(<number> Starting Index, <number> Length)
This function returns new series containing a subset of the calling series beginning at Starting Index and continuing for Length number of samples. Both arguments are defined in samples.
Example:
var mySubset = mySeries.subset(750, 500);
The example above creates a series that is 500 samples long, and represents samples 750-1250 in the calling series.