User`s guide

tfdata
11-231
11tfdata
Purpose Quick access to transfer function data
Syntax [num,den] = tfdata(sys)
[num,den] = tfdata(sys,'v')
[num,den,Ts] = tfdata(sys)
Description [num,den] = tfdata(sys) returns the numerator(s) a nd denominator(s) of
the transfer function for the TF, SS or ZPK model (or LTI array of TF, SS or
ZPKmodels)
sys. Forsingle LTI models,theoutputs num andden of tfdata are
cell arrays with the following characteristics:
•
num and den have as many rows as outputs and as many columns as inputs.
• The
(i,j) entries num{i,j} and den{i,j} are row vectors specifying the
numerator and denominator coefficients of the transfer function from input
j to output i. These coefficients are ordered in descending powers of or .
For arrays
sys of LTI models, num and den are multidimensional cell arrays
with the same sizes as
sys.
If
sys is a state-space or zero-pole-gain model, it is first converted to transfer
function form using
tf. See Table 11-15, “LTI Properties,” on page 11-195 for
more information on the format of transfer function model data.
For SISO t ransfer functions, the syntax
[num,den] = tfdata(sys,'v')
forcestfdata to return the numeratorand denominator directlyas row vectors
rather than as cell arrays (see example below).
[num,den,Ts] = tfdata(sys) also returns the sample time Ts.
You can access the remaining LTI properties of
sys with get or by direct
referencing, for example,
sys.Ts
sys.variable
Example Given the SISO transfer function
h = tf([1 1],[1 2 5])
s
z