Function Reference    

Quick access to transfer function data



[num,den] = tfdata(sys) returns the numerator(s) and denominator(s) of the transfer function for the TF, SS or ZPK model (or LTI array of TF, SS or ZPK models) sys. For single LTI models, the outputs num and den of tfdata are cell arrays with the following characteristics:

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 11-194 for more information on the format of transfer function model data.

For SISO transfer functions, the syntax

forces tfdata to return the numerator and denominator directly as 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,


Given the SISO transfer function

you can extract the numerator and denominator coefficients by typing

This syntax returns two row vectors.

If you turn h into a MIMO transfer function by typing

the command

now returns two cell arrays with the numerator/denominator data for each SISO entry. Use celldisp to visualize this data. Type

and MATLAB returns the numerator vectors of the entries of H.

Similarly, for the denominators, type

See Also
get         Get properties of LTI models

ssdata      Quick access to state-space data

tf          Specify transfer functions

zpkdata     Quick access to zero-pole-gain data

  tf totaldelay