Matlab GUI: how to print slider value to workspace

Hello I am having some issue with my GUI. I am trying to set up a slider to create a time vector between two point. I have two sliders and will use one value and subtract the other value to create a time vector. Here is my GUI:

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

% Last Modified by GUIDE v2.5 26-Apr-2017 09:25:59

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @Drive_Cycle_GUI_OpeningFcn, ...
                   'gui_OutputFcn',  @Drive_Cycle_GUI_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 Drive_Cycle_GUI is made visible.
function Drive_Cycle_GUI_OpeningFcn(hObject, ~, handles, varargin)
% This function has no output args, see OutputFcn.

    if true
      % code
    end
  % 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 Drive_Cycle_GUI (see VARARGIN)

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

% Update handles structure
guidata(hObject, handles);

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

% --- Outputs from this function are returned to the command line.
function varargout = Drive_Cycle_GUI_OutputFcn(~, ~, 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} = get(handles.output);

% --- Executes on mouse press over axes background.
function axes1_ButtonDownFcn(hObject, eventdata, handles)
% hObject    handle to axes1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% --- 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)
axes(handles.axes2);
S.HWFET = xlsread('DriveCycles_Scaled.xlsx',5,'A4:B769');
S.LN = plot(S.HWFET(:,1),S.HWFET(:,2),'r');
S.leftmarker =  line([0 0],get(handles.axes2,'Ylim'));
S.rightmarker = line([0 0],get(handles.axes2,'Ylim'));
S.sl_left = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 380 260 30],...
                 'min',1,'max',length(S.HWFET),'val',1,...
                 'sliderstep',[1/765 1/765],...
                 'callback',{@sl_left_call,S});
S.sl_right = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 320 260 30],...
                 'min',1,'max',length(S.HWFET),'val',1,...
                 'sliderstep',[1/765 1/765],...
                 'callback',{@sl_right_call,S});  
axes(handles.axes3)
car = importdata('Car_Graphic.jpg');
image(car);
axis off

% --- 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.axes2);
S.FTP = xlsread('DriveCycles_Scaled.xlsx',4,'A4:B2481');
S.LN = plot(S.FTP(:,1),S.FTP(:,2),'r');
S.leftmarker =  line([0 0],get(handles.axes2,'Ylim'));
S.rightmarker = line([0 0],get(handles.axes2,'Ylim'));
S.sl_left = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 380 260 30],...
                 'min',1,'max',length(S.FTP),'val',1,...
                 'sliderstep',[1/2477 1/2477],...
                 'callback',{@sl_left_call,S});
S.sl_right = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 320 260 30],...
                 'min',1,'max',length(S.FTP),'val',1,...
                 'sliderstep',[1/2477 1/2477],...
                 'callback',{@sl_right_call,S});  
axes(handles.axes3)
car = importdata('Car_Graphic.jpg');
image(car);
axis off

% --- Executes on button press in pushbutton3.
function pushbutton3_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
axes(handles.axes2);
S.US06 = xlsread('DriveCycles_Scaled.xlsx',6,'A4:B600');
S.LN = plot(S.US06(:,1),S.US06(:,2),'r');
S.leftmarker =  line([0 0],get(handles.axes2,'Ylim'));
S.rightmarker = line([0 0],get(handles.axes2,'Ylim'));
S.sl_left = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 380 260 30],...
                 'Tag', 'LeftSlider',...
                 'min',1,'max',length(S.US06),'val',1,...
                 'sliderstep',[1/596 1/596],...
                 'callback',{@sl_left_call,S});
S.sl_right = uicontrol('style','slide',...
                 'unit','pix',...
                 'position',[575 320 260 30],...
                 'min',1,'max',length(S.US06),'val',1,...
                 'sliderstep',[1/596 1/596],...
                 'callback',{@sl_right_call,S});  
axes(handles.axes3)
car = importdata('Car_Graphic.jpg');
image(car);
axis off

function sl_left_call(varargin)
% Callback for the slider.
[h,S] = varargin{[1,3]};  % calling handle and data structure.
set(S.leftmarker,'Xdata',[get(h,'value') get(h,'value')])
%  setappdata(S.leftmarker,'leftposition','value')
%  getappdata(S.leftmarker,'leftposition')

function [] = sl_right_call(varargin)
% Callback for the slider.
[h,S] = varargin{[1,3]};  % calling handle and data structure.
set(S.rightmarker,'Xdata',[get(h,'value') get(h,'value')])

Right now everything works except not printing, I am in need of help on this part. I am pretty new to Matlab GUI.

Thank you

[Jan]

The question is not clear: In which part of this code do you try to create a "time vector". By the way, what is a "time vector"? What does "printing to Workspace" exactly mean? When should what appear where?

[Tyler Martin]

So in the slider callback, I would like to take the current value of the slider and put it on the workspace

[Adam]

Why? The whole point of a GUI is to use its own workspace. If you are going to put the value into the main workspace anyway you might as well just type it in!

[Tyler Martin]

I am using the GUI as part of a larger app that calls for the user input of the sliders to made a vector to be used in another M File

[Adam]

Is there a reason you can't just call the other m-file from a GUI callback?

[Tyler Martin]

Can you explain that?

[Adam]

You can put any code in e.g. pushbutton3_Callback that you could put on the command line so that is the usual way to respond to changes on the UI and have relevant code be automatically called rather than just dump parameters into the base workspace and wait for the functionality to be called afterwards from there. It seems to defeat the purpose of having a UI.

Answer 1

[Jan]

Using the base workspace to collect data is a bad idea. It suffers from the same problems as global variables (ask a search engine for details).

The standard way to solve this is to collect values inside a GUI (search for "share data between callbacks" in this forum) and start the calculations e.g. by a button. Then you can run multiple instances of the GUI or different GUIs with interferences.

You create the sliders dynamically inside the callback. This will be very confusing, if the button is pressed mutiple times.