MATLAB: How to specify two damping ratio (zeta) values for s-plane grid lines for a root locus

grid linesroot locuss-planesgrid

I would like to include two grid lines on my root locus. Essentially, I would like to show the bounds of 'good' gain values which occur between two zeta values.
Ideally the code would look simply as:
rlocus(sys)
sgrid(z1,0)
sgrid(z2,0)
And both of zeta grid lines would appear. However this does not work. //I would appreciate any help. Thanks.

Best Answer

I have figured it out.
Zeta is in fact a vector, and can thus have multiple values in its array.
The solution to my problem, for anyone interested is the following:
z = [z1 z2]
rlocus(sys)
sgrid(z,0)
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