gnuplot basics
Best, simplest, very powerful plotter (and more)
Can easily plot formulas or data_files or both! few plotters can do it so simply!
gnuplot> plot "File"   will plot column 1 as x , col 2 as y of a file named "File"
  or can specify which columns of multicolumn file:
gnuplot> plot "File" u 3:1 w lines lt 1 lw 2
  will plot using column 3 as x and 1 as y   with lines, in red (lt 1), line_width 2

  • Can plot formulas directly:
    gnuplot> R(x) = 1/(1+x**2)     formula to plot (Runge function)
    gnuplot> plot R(x)     default xrange is [-10:10]
    Can specify desired xrange [-5:5] , in blue (lt 3), lw 4:
    gnuplot> plot [-5:5] R(x) lt 3 lw 4

  • Can plot several graphs on same plot:
    formulas, and/or formulas and files: use comma in-between:   plot "file" , R(x) , ...   e.g.
    gnuplot> G(x) = exp(-x**2)     another formula to plot (Gaussian, bell curve)
    gnuplot> plot R(x) , G(x)   (on default xrange, default colors)
    Better: specify xrange, colors, line_widths:
    gnuplot> plot [-5:5] R(x) lt 1 lw 3, G(x) lt 2 lw 4
    Set xlabel, ylabel, title:
    gnuplot> set xlabel 'x' ; set ylabel 'y'
    gnuplot> set title 'Runge R(x) and Gaussian G(x)'
    gnuplot> replot     (re-plot last plot)

    See links on course page for more...