Introduction to GnuPlot

from: http://learn.tsinghua.edu.cn/homepage/2001315450/gnuplot-doc/TOC.html

1, Variables and Functions

In 2D plots, the variable to use is x, in 3D plots, use x and y. Multiplication is denoted by *, and division by /. Exponents are denoted by**, and all multiplication must be explicit. That is, 3x would generate and error, you would want to use 3*x.

• The standard trig functions, sin, cos, and tan Note, to use the constant pi can be referenced by just using pi.
• The inverse trig functions , asin, acos, and atan.
• The hyperbolic trig functions, sinh, cosh, and tanh.
• The exp and log function. exp raises e to the power of its argument. For example, 4e^2x would be 4*exp(2*x) in Gnuplot. log returns the natural log (base e) of it's argument. This corresponds to ln in normal math notation.
• For information on other functions, type help functions in Gnuplot.

2, 2-D plot:

• plot

To change the scale, use one of the following forms of plot:

• plot [x1:x2] [y1:y2]
• plot [x1:x2] (To just set the x range)
• plot [] [y1:y2] (To just set the y range).

To set the default x range back to [-10,10], type the following:

• set xrange [-10:10]

Also, if you set the range for the y values, they will stay the same for future plots as well. You can set GnuPlot back to autoscaling the y axis by typing the following:

• set autoscale y

3, 3-D plot:

• splot
• splot [x1:x2] [y1:y2] [z1:z2]
• splot [x1:x2] (To just set the x range)
• splot [] [y1:y2] (To just set the y range).
• splot [] [] [z1:z2] (To just set the y range).

hide the grid points on the drawing graph.

• set hidden3d
• replot

Increasing Precision of 3D plots

• set isosamples x_rate, y_rate

Adding contour line

• set contour base - Draw the contour lines along the base of the diagram
• set contour surface - Draws the lines along the 3D surface
• set contour both - Draws lines on both surface and base
• set nocontour - Turns off contour lines

Changing view of graph

• set view horizontal_angle,vertical_angle

• set view horizontal_angle,vertical_angle,zoom
• set view ,,zoom

4, Parametric Equations

• set parametric

To go back to standard Cartesian mode, type:

• set noparametric

To switch to graphing with polar coordinates, type:

• set polar

To switch back to Cartesian coordinates, type:

• set nopolar

Plotting Data

# Example1.dat
# number of subint.   - width of subinterval, computed value, abs. error
0 1   5   0.00673794699908559

plot "example1.dat"

• set logscale
• set data style linespoints
• replot

Change the plot's columns:

• set nologscale
• plot "example1.dat" using 1:3

3-D data plots:

• set parametric
• set data style lines
• splot "try2.dat"

Outputs:
ps file:

• set output "filename.ps" where filename.ps is the name of the output file.
• set terminal postscript
• replot

eps file:

• set output "filename.eps"
• set terminal postscript eps

Load from a file:

• load 'work.gnu'

Line styles:
You can also add the with keywork to plot and splot commands. For example,

• plot sin(x) with boxes
• plot "turkey.dat" with impulses

The following line styles are available for 2D function and data plots: `lines`, `points`, `linespoints`, `impulses`, `dots`, `steps`, `errorbars`, `boxes`, and `boxerrorbars`

Define new variables and Functions:

• constant_name = expression
• function-name(parameters) = expression

Add time and title:

• set time
• set title "Farm Data Plot"
• set nokey