set datafile separator {whitespace | tab | comma | "chars"}
"csv" is short for "comma-separated values". The term "csv file" is loosely applied to files in which data fields are delimited by a specific character, not necessarily a comma. To read data from a csv file you must tell gnuplot what the field-delimiting character is. For instance to read from a file using semicolon as a field delimiter:
set datafile separator ";"
See set datafile separator (p. ). This applies only to files used for input.
To create a csv file on output, use the corresponding separator option to
set table.