%% Valid Structures of Lowpass Filter
% Design a default lowpass filter specification object. Return all valid design methods and structures in a structure array. Display the fieldnames to see all valid design methods. Display the valid filter structures for the equiripple field.

D = fdesign.lowpass;
filtstruct = validstructures(D);
fieldnames(filtstruct)

%

filtstruct.equiripple

%
% If you have the DSP System Toolbox™ software installed, use the 'SystemObject', sysobjflag syntax to return valid structures for a filter System object™.

filtstruct = validstructures(D,'butter','SystemObject',true)

% Copyright 2012 The MathWorks, Inc.