Practical 7: Symbolic Toolbox

• array of $x$- coordinates
• array of $y$- coordinates

• function handle
• endpoints

• symbolic function
• endpoints

• does not need a function formula
• full control of graph parameters

• function is stored in M-file for easy access (via handle) and modification

• can easily create a graph using only two lines of code

• requires more code to generate

• must create a function M-file if it is not MATLAB in-build function

• function is not stored in easily accessible M-file,
• graphs have the same colour

Example:

Create a graph of the function

Which plot command would you use?

Answer:

The answer depends on your overall task.

If you will need this function for further calculations, then use fplot command. To use fplot, you will need to create a function M-file, specifying the three parts of the function separately by using if statements.

If you want just to plot this function, then use ezplot with hold on and hold off commands to plot it ‘piece-by-piece’, specifying endpoints.

clear all

syms x

hold on

ezplot(x,[-2, 0])

ezplot(2*x,[0, 1])

ezplot(3*x,[1, 2])

axis([-2 2 -2 6])            %why do you need to do this?

title(‘Piece-wise function’) %what changes will happen if you delete this command?

hold off

Note: If you plot several functions using ezplot, then the title of the figure will be of the last function plotted. The hardest option for this sort of function is to use the plot command. Otherwise, all the above options are relatively same.

Quickly check that the equation $speed=20ln(t+1)$ accurately reflects the speed of a car for $t$ between 0 and 10 seconds.

Hint: use ezplot.

> Exercise: Graphing

> In the table below you are given the results of a student’s weekly assignments to plot.

> Which graphing technique would you use in this case?