MATLAB® and Its Applications in Engineering: [Based on MATLAB 7.5 (R2007b)]

12.4. Root Locus Using plot Command

To obtain the roots of characteristic equation for values of K specified by the user, the following commands can be used:

[r, K] = rlocus (n, d)

or

[r, K] = rlocus (n, d, K)

These commands will return matrix r containing the values of roots of the characteristic equation for the corresponding values of K.

The root locus plot can also be obtained by using plot command for matrix r obtained as outlined above and is as shown below:

r = rlocus (n, d);
plot (r, ' ');

The plot command plots the root locus. Different line styles can be used in these plots. To plot the root loci with marks ‘o’ or ‘x’, the commands plot (r, 'o') or plot (r, 'x') can be used.

Example 12.4.

Plot root locus and examine the stability ...