The string function gprintf("format",x) uses gnuplot's own format specifiers,
as do the gnuplot commands set format, set timestamp, and others. These
format specifiers are not the same as those used by the standard C-language
routine sprintf(). gprintf() accepts only a single variable to be formatted.
Gnuplot also provides an sprintf("format",x1,x2,...) routine if you prefer.
For a list of gnuplot's format options, see format specifiers (p. ).