Control System Toolbox Function Reference

frdata

Quick access to data for a frequency response data object

Syntax

[response,freq] = frdata(sys)
[response,freq,Ts] = frdata(sys)
[response,freq] = frdata(sys,'v')

Description

[response,freq] = frdata(sys) returns the response data and frequency samples of the FRD model sys. For an FRD model with Ny outputs and Nu inputs at Nf frequencies:

• response is an Ny-by-Nu-by-Nf multidimensional array where the (i,j) entry specifies the response from input j to output i.
• freq is a column vector of length Nf that contains the frequency samples of the FRD model.

See Table 11-14, "Data Format for the Argument response in FRD Models," on page 80 for more information on the data format for FRD response data.

For SISO FRD models, the syntax

[response,freq] = frdata(sys,'v')

forces frdata to return the response data and frequencies directly as column vectors rather than as cell arrays (see example below).

[response,freq,Ts] = frdata(sys) also returns the sample time Ts.

Other properties of sys can be accessed with get or by direct structure-like referencing (e.g., sys.Units).

Arguments

The input argument sys to frdata must be an FRD model.

Example

Typing the commands

freq = logspace(1,2,2);
resp = .05*(freq).*exp(i*2*freq);
sys = frd(resp,freq);
[resp,freq] = frdata(sys,'v')

returns the FRD model data

resp = 
    0.2040 + 0.4565i
   2.4359 - 4.3665i
freq =
    10
   100

See Also
frd         Create or convert to FRD models

get         Get the properties for an LTI model

set         Set model properties

frd

freqresp