The command `set datafile separator "<char>"` tells `gnuplot` that data fields in subsequent input files are separated by <char> rather than by whitespace. The most common use is to read in csv (comma-separated value) files written by spreadsheet or database programs. By default data fields are separated by whitespace.
Syntax:
set datafile separator {"<char>" | whitespace}
Examples:
# Input file contains tab-separated fields
set datafile separator "\t"
# Input file contains comma-separated values fields
set datafile separator ","