function varargout = IIRimpv(varargin)
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @IIRimpv_OpeningFcn, ...
                   'gui_OutputFcn',  @IIRimpv_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin & isstr(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

function IIRimpv_OpeningFcn(hObject, eventdata, handles, varargin)
handles.output = hObject;
guidata(hObject, handles);

function varargout = IIRimpv_OutputFcn(hObject, eventdata, handles)
varargout{1} = handles.output;

function edit1_CreateFcn(hObject, eventdata, handles)

if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end
function edit1_Callback(hObject, eventdata, handles)
N = str2num(get(hObject, 'String'));
data = getappdata(gcbf, 'UserData');
data.N = N;
setappdata(gcbf, 'UserData', data);

function edit2_CreateFcn(hObject, eventdata, handles)

if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end

function edit2_Callback(hObject, eventdata, handles)
Wn= str2num(get(hObject, 'String'));
data = getappdata(gcbf, 'UserData');
data.Wn = Wn;
setappdata(gcbf, 'UserData', data);

function edit4_CreateFcn(hObject, eventdata, handles)

if ispc
    set(hObject,'BackgroundColor','white');
else
    set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end

function edit4_Callback(hObject, eventdata, handles)
Fs = str2num(get(hObject, 'String'));
data = getappdata(gcbf, 'UserData');
data.Fs = Fs;
setappdata(gcbf, 'UserData', data);

function pushbutton1_Callback(hObject, eventdata, handles)
data = getappdata(gcbf, 'UserData');
[num,den]=butter(data.N,data.Wn,'s');
%
%	Convert analogue filter into Discrete IIR filter
%
[b, a]=impinvar(num, den, data.Fs);		%Determine coeffs of IIR filter
subplot(2,1,2)				% Plot magnitude freq. response
[h, omega]=freqz(b, a, 512);			
mag = 20*log10(abs(h))
plot(omega/pi,mag);grid;
xlabel('Normalized Frequency ')
ylabel('Gain dB')
