Version 4 of gnuplot is much less sensitive than earlier versions to the order of keywords and suboptions. However, if you get error messages from specifying options that you think should work, please try rearranging them into the exact order listed by the documentation.
Options and any accompanying parameters are separated by spaces whereas lists and coordinates are separated by commas. Ranges are separated by colons and enclosed in brackets [], text and file names are enclosed in quotes, and a few miscellaneous things are enclosed in parentheses. Braces {} are used for a few special purposes.
Commas are used to separate coordinates on the `set` commands arrow, `key`, and `label`; the list of variables being fitted (the list after the `via` keyword on the fit command); lists of discrete contours or the loop parameters which specify them on the cntrparam command; the arguments of the `set` commands dgrid3d, dummy, isosamples, offsets, origin, samples, size, `time`, and view; lists of tics or the loop parameters which specify them; the offsets for titles and axis labels; parametric functions to be used to calculate the x, y, and z coordinates on the `plot`, replot and `splot` commands; and the complete sets of keywords specifying individual plots (data sets or functions) on the `plot`, replot and `splot` commands.
Parentheses are used to delimit sets of explicit tics (as opposed to loop parameters) and to indicate computations in the using filter of the fit, `plot`, replot and `splot` commands.
(Parentheses and commas are also used as usual in function notation.)
Square brackets are used to delimit ranges given in `set`, `plot` or `splot` commands.
Colons are used to separate extrema in `range` specifications (whether they are given on `set`, `plot` or `splot` commands) and to separate entries in the using filter of the `plot`, replot, `splot` and fit commands.
Semicolons are used to separate commands given on a single command line.
Braces are used in text to be specially processed by some terminals, like `postscript`. They are also used to denote complex numbers: {3,2} = 3 + 2i.
At present you should not embed \n inside {} when using the PostScript terminal in `enhanced text` mode.
The EEPIC, Imagen, Uniplex, LaTeX, and TPIC drivers allow a newline to be specified by \\ in a single-quoted string or \\\\ in a double-quoted string.