ZF - Zero filling (nmrPipe function)
From NMR Wiki
Zero filling function adds zeros to the data vectors to either increase digital resolution or prepare the data for the Hilbert transformation.
The function can also be used to truncate data vectors.
Note that final data size of n = 2i, where i is integer speeds up the fourier transformation.
Examples
Add zeros or remvove data points from the end of vectors to final size of 256 points
nmrPipe -fn ZF -size 256