Undefined Operators for input arguments of type 'struct'?

Basically I want the user defined inputs to be considered and for the calculations and for the pushbutton to carry out the plotting. Sit tight because there is A LOT of problems in this code:

function varargout = CEN320Project(varargin)
% CEN320PROJECT MATLAB code for CEN320Project.fig
%      CEN320PROJECT, by itself, creates a new CEN320PROJECT or raises the existing
%      singleton*.
%
%      H = CEN320PROJECT returns the handle to a new CEN320PROJECT or the handle to
%      the existing singleton*.
%
%      CEN320PROJECT('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in CEN320PROJECT.M with the given input arguments.
%
%      CEN320PROJECT('Property','Value',...) creates a new CEN320PROJECT or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before CEN320Project_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to CEN320Project_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help CEN320Project

% Last Modified by GUIDE v2.5 03-Dec-2019 02:50:00

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @CEN320Project_OpeningFcn, ...
                   'gui_OutputFcn',  @CEN320Project_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(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


% --- Executes just before CEN320Project is made visible.
function CEN320Project_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to CEN320Project (see VARARGIN)

% Choose default command line output for CEN320Project
handles.output = hObject;
handles.edit1=0;
handles.edit2=0;
% Update handles structure
guidata(hObject, handles);

% UIWAIT makes CEN320Project wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = CEN320Project_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Get default command line output from handles structure
varargout{1} = handles.output;


% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
handles.edit1=handles.edit1 +1
handles.edit2=handles.edit2 +1
guidata(hObject,handles)
N=guidata(hObject)
time=guidata(hObject)
recObj = audiorecorder(1000,16, 1);  
record_time = 5;
recordblocking(recObj, record_time);
myECG = getaudiodata(recObj);
save('mydata')
y=myECG
Y=fft(myECG); 
mag=abs(Y);
fs=500;
ecg=y(); 
for k=1:N;
ang(k) = inv(tan(imag(Y(k))/real(Y(k))*pi/180));
end
sum=0;
t=0:0.01:N;
for h=1:N
sum=sum+Y(h)*exp(1i*2*pi*(500/N)*t);
end



axes(handles.axes1)
plot(t,myECG)
title('ECG Signal')
xlabel('t')
ylabel('Amplitude')
grid on
axes(handles.axes2)
plot(t,mag)
title('Magnitude Spectrum')
xlabel('n')
ylabel('Magnitude')
grid on
axes(handles.axes3)
plot(t,ang)
title('Phase Spectrum')
xlabel('n')
ylabel('Angle')
grid on

function edit1_Callback(edit1, eventdata, handles)
% hObject    handle to edit1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
N=str2double(get(edit1,'string'));
assignin('base','N',str2double(get(edit1,'string')));

% Hints: get(hObject,'String') returns contents of edit1 as text
%        str2double(get(hObject,'String')) returns contents of edit1 as a double


% --- Executes during object creation, after setting all properties.
function edit1_CreateFcn(edit1, eventdata, handles)
% hObject    handle to edit1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(edit1,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(edit1,'BackgroundColor','white');
end



function edit2_Callback(edit2, eventdata, handles)
% hObject    handle to edit2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
time=str2double(get(edit2,'string'));
assignin('base','time',str2double(get(edit2,'string')));
% Hints: get(hObject,'String') returns contents of edit2 as text
%        str2double(get(hObject,'String')) returns contents of edit2 as a double


% --- Executes during object creation, after setting all properties.
function edit2_CreateFcn(edit2, eventdata, handles)
% hObject    handle to edit2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    empty - handles not created until after all CreateFcns called

% Hint: edit controls usually have a white background on Windows.
%       See ISPC and COMPUTER.
if ispc && isequal(get(edit2,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(edit2,'BackgroundColor','white');
end

So this undefined operator error keeps showing up:

Undefined operator ':' for input arguments of type 'struct'.

Error in CEN320Project>pushbutton1_Callback (line 97)
for k=1:N

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in CEN320Project (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)CEN320Project('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

if I get rid of the colon ":" then it says undefined operator "/", so I guess I have a bunch of "undefined operators" for struct type input arguments whatever that means. and if there is no calculations at all it says error using plot, not enough input arguments, How do I get the pushbutton to carry out these calculations and plots.

[Stephen23]

The variable N is a copy of the structure handles:

function pushbutton1_Callback(hObject, eventdata, handles)
...
guidata(hObject,handles)
N=guidata(hObject)
...
for k=1:N;

So your code is basically equivalent to:

function pushbutton1_Callback(hObject, eventdata, handles)
...
N=handles
...
for k=1:N;

What do you expect the colon operator to do with a structure?

[Momen Elhassan]

so then how do I carry the value of the "N" from the edit box and have it be defined and ready to use for the push button?