82 CHAPTER 3. FUNCTIONAL DESCRIPTION OF Xµ
3.3.2 Formatted Display Functions
It is often useful to consider complex numbers in terms of frequency and damping. This
is particularly applicable when studying the poles or zeros of a system. Thecommand
rifd provides a real-imaginary-frequency-damping formatted display for complex valued
input. The following example illustrates the most common usage.
# display the poles locations of system: sys1
rifd(poles(sys1))
Using the keyword {discrete}will give the display in terms of z-plane rather than the
s-plane. If the input to rifd is a Dynamic System then both the poles and zeros are
calculated and displayed.
3.3.3 Plotting Functions
As pdms are a native data object in Xmath, the standard Xmath plot function will
correctly plot a pdm. Multiple pdms over differing domains can be handled with
repeated calls to the plot function by using the graphical object created from the
previous plot call. The Xmath Basics manual describes this feature in detail.
The Xµfunction ctrlplot provides more control system specific plotting capabilities.
Keywords allow the user to easily specify Bode, Nyquist, Nichols and other plots.
Because it handles graphic objects in a similar manner to plot, the resulting plots can
be modified by subsequent plot function calls. An example is given below.
sys1 = 1/makepoly([1,1],"s")
sys2 = 2*sys1*10/makepoly([1,1,10],"s")
w1 = logspace(0.01,10,50)’
w2 = sort([w1;[0.35:0.01:0.65]’])
sys1g = freq(sys1,w1)
sys2g = freq(sys2,w2)
# Bode plots