Calling a function using a Matlab GUI pushbutton

Question

I'm trying to call a function qrsdet(vecParam1,scaParam1,scaParam2) in GUIDE using a pushbutton startAnalysis. Here is the code:

GUI CODE:

% --- Executes just before GUIforUser is made visible.
function GUIforUser_OpeningFcn(hObject, eventdata, handles, varargin)

handles.output = hObject;
guidata(hObject, handles);

-------
% remaining GUI code
-------

% pushbutton code to call function
function qrsdetfn_Callback(hObject, eventdata, handles)

hr = qrsdet(vecArg1,scaArg1,scaArg2);
textLabel = sprintf('%.2f', hr);
set(handles.heartratetext, 'String', hr);
guidata(hObject,handles)

I have defined a .m file called qrsdet.m, which resides in the same directory as my GUI. All three arguments are acquired from the user using the GUI. The issue is when I pass the arguments to my function I get the error:

Undefined function or variable 'vecArg1'.

I have stored vecArg1 in the handles structure in the matlab GUI. I've even tried using the following statement:

qrsdet(handles.vecArg1,scaArg1,scaArg2)

but this returns the error:

Reference to non-existent field 'vecArg1'

This is the pushbutton I'm using to load vecArg1

% --- Executes on button press
function pushbtnForvecArg1_Callback(hObject, eventdata, handles)

handles.fileloc = get(handles.filelocation,'String');
fileID = fopen(handles.fileloc);
handles.vecArg1 = fscanf(fileID,'%f',inf);
assignin('base','vecArg1',handles.vecArg1);
guidata(hObject,handles)

I'm pretty new to GUI design in Matlab, any pointers to what might be the issue?

Answer 1

I believe the problem is your input parameters.

When you start any function in MATLAB, your variables must be assigned a value. MATLAB GUIDE will not allow for variables to be used in the means that you have used vecArg1, vecArg2, and vecArg3. It essentially thinks that you have used a variable which does not exist.

I think the following code may work for you.

Set your variables using:

setappdata(hObject.Parent, 'vecArg1', desired_value_to_be_stored);

This will allow you to use the following code in a different section of the GUIDE file to retrieve this data:

data_to_be_used = getappdata(hObject.Parent, 'vecArg1');

It's a bit tedious but it should work.

~~~~~~~~~~~~~~~~~~~~~~~~

EDIT1: Demonstration of use of setappdata and getappdata

GUIDE m-file, the figurecontains:

pushbutton1 -> get the data & test

pushbutton2 -> set the data

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

% Last Modified by GUIDE v2.5 10-Apr-2016 15:17:00

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

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

% Update handles structure
guidata(hObject, handles);

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


% --- Outputs from this function are returned to the command line.
function varargout = gui_example_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)

status = printvector(getappdata(hObject.Parent, 'vecArg1'));

disp(status);

% --- 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)


%Set vector argument
vectorArgument1 = [1.001; 1.002; 1.003; 1.004];
setappdata(hObject.Parent, 'vecArg1', vectorArgument1);

Function called on button press:

function [ status ] = printvector( vec1 )
    disp('I am in the function')
    for i = 1:length(vec1)
        disp(vec1(i,1));
    end

    status = 'success';
end