How can I load and plot a signal with GUI MATLAB?

Hi all,

I want to load a signal ('.mat') from my pc and when I push the Plot button, plot it. I wrote the following codes but I have the errors

Error using plot
Invalid first data argument.

Error in readfile>pushbutton2_Callback (line 95)
plot(handles.signal)

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

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

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)readfile('pushbutton2_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback"

Here's the code.

function varargout = readfile(varargin)
% READFILE MATLAB code for readfile.fig
%      READFILE, by itself, creates a new READFILE or raises the existing
%      singleton*.
%
%      H = READFILE returns the handle to a new READFILE or the handle to
%      the existing singleton*.
%
%      READFILE('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in READFILE.M with the given input arguments.
%
%      READFILE('Property','Value',...) creates a new READFILE or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before readfile_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to readfile_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 readfile

% Last Modified by GUIDE v2.5 25-Apr-2019 10:20:12

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @readfile_OpeningFcn, ...
                   'gui_OutputFcn',  @readfile_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 readfile is made visible.
function readfile_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 readfile (see VARARGIN)

% Choose default command line output for readfile
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

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


% --- Outputs from this function are returned to the command line.
function varargout = readfile_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)
[filename pathname]=uigetfile({'*.mat'}, 'File Browser');
fullpathname=strcat(pathname, filename);
signal=fileread(fullpathname);
set(handles.text3,'String',fullpathname);
handles.signal = signal;
guidata(hObject, handles);


% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
axes(handles.axes1)
plot(handles.signal)

I was wondering if you could help me. Tnx

[Adam]

fileread returns a char vector. This is not a valid argument to the plot command.

[Mohammad Shahbakhti]

So what command should I use instead?

[Mohammad Shahbakhti]

I used 'load' command instead. But I have these errors

Error using plot
Not enough input arguments.

Error in readfile>pushbutton2_Callback (line 95)
plot(handles.signal)

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

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

Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)readfile('pushbutton2_Callback',hObject,eventdata,guidata(hObject)) 
Error while evaluating UIControl Callback.

[Walter Roberson]

handles might be an empty struct array at that point, or handles.signal might not be of expected data type.

If you did

signal = load(fullpathname);

where fullpathname names a .mat file, then signal would not be the data directly: it would be a struct with one field for each variable stored in the .mat file.

[Mohammad Shahbakhti]

I am a bit confused now!! So what commmands should I use to load the data? with my code, there is Browser botton which you can load the data from PC. The problem is about plotting error. I was wondering if you could help me to solve this problem. Tnx

[Adam]

You can use the debugger to check that your data has been loaded as expected first, and that it is available to you in the Pushbutton2 callback. Then the plot error should become obvious.

Answer 1

[Walter Roberson]

datastruct = load(fullpathname);
%we will assume that the data is in the first variable in the
% .mat file, no matter what it is named.
fn = fieldnames(datastruct);
signal = datastruct.(fn{1})

[Mohammad Shahbakhti]

Tnx a lot. It worked. <3