Specifying Functions in Gnuplot

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.

For example, the polynomial 3x⁴ + 4x - 2/3 would be the following in Gnuplot:

3*x**4 + 4*x - 2/3

Gnuplot also has a number of predefined functions. These are called by putting the arguments in parenthesis, i.e., sin(x). These include the following:

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.

The following are other examples of functions. Make sure you understand what functions are being described.

(x**2 - 4)/(x +2)
x**2 + y**2 - (x*y)**(2/3)
log(exp(x)) (Hint, this simplifies to x)
sin(x*y)
3*x**2 + 6/(1*y**2)

Table of Contents - Previous - Starting and Quitting GnuPlot - Next - A Simple Example

College of Natural Sciences / University of Northern Iowa / [email protected]