Many experiments involve collecting data in trials and varying one or more parameters across trials. The ndata analysis system can help you group trials together that share common parameter values. How trials are grouped is determined by the second non-comment line in the nda script, known as the grouping line.

The grouping line must take one of the following forms:

The names of parameters that vary across trials in the ndata file are known as var params. The var param names can be determined by using the ndata application program to browse the data file.