Asked by Hassan Bosha
on 16 Feb 2019

this an example of a slider to control movement on axes

a = get (handles.slider2,'Value')

x = 0:0.1:50;

y = sin (x*a);

plot (handles.axes1,x,y)

and this me trying to apply the example

function slider2_Callback(hObject, eventdata, handles)

% hObject handle to slider2 (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'Value') returns position of slider

% get(hObject,'Min') and get(hObject,'Max') to determine range of slider

clc;

load ('100m.mat')

a = get(handles.slider2,'Value');

x = 0:0.1:50;

ECGsignal = (val - 1024 )/200;

y = ECGsignal*x*a;

plot (handles.axes1,x,y)

what is the problem in my code ?

Answer by Rik
on 19 Feb 2019

Accepted Answer

Instead of scaling the data, this code changes the axis limits.

%generate some data and set the x window size

x=linspace(0,50,1000);

y=sin(exp(x/10));

xwindow_size=20;

xwindow_min=min(x);

xwindow_max=max(x);

%make the GUI

h=struct;

h.f=figure(1);

clf(h.f)%make sure the figure is empty, not needed if you use h.f=figure;

h.xwindow_size=xwindow_size;

h.xwindow_min=xwindow_min;

h.xwindow_max=xwindow_max;

h.ax=axes('Parent',h.f,...

'Units','Normalized',...

'Position',[0.1 0.3 0.8 0.6]);

h.slider=uicontrol('Parent',h.f,...

'Style','slider',...

'Value',h.xwindow_min+h.xwindow_size/2,...

'min',h.xwindow_min+h.xwindow_size/2,...

'max',h.xwindow_max-h.xwindow_size/2,...

'Units','Normalized',...

'Position',[0.1 0.1 0.8 0.1],...

'Callback',@sliderCallback);

guidata(h.f,h)

%make the plot

plot(x,y,'Parent',h.ax)%create the plot itself

%set(h.ax,'YLim',[min(y) max(y)])%fix the y-axis to specific values

set(h.ax,'YLim',[-1 1])%fix the y-axis to specific values

sliderCallback(h.f)%initialize the x-axis

function sliderCallback(obj,evnt)

handles=guidata(obj);

a=get(handles.slider,'Value');

set(handles.ax,'XLim',[-0.5 0.5]*handles.xwindow_size+a)

end

Hassan Bosha
on 19 Feb 2019

That's perfect , all i need is to fit it on the my GUI Code , any idea how ?

Hassan Bosha
on 19 Feb 2019

% --- Executes on slider movement.

function slider4_Callback(hObject, eventdata, handles)

load ('100m.mat')

y = (val - 1024 )/200;

Fs = 360;

x = (0:length(y)-1)/Fs ;

xwindow_size=1;

%set(h.ax,'YLim',[min(y) max(y)])%fix the y-axis to specific values

set(h.ax,'YLim',[floor(min(y)) ceil(max(y))])%fix the y-axis to specific values

handles=guidata(hObject);

a=get(handles.slider,'Value');

set(handles.ax,'XLim',[-0.5 0.5]*handles.xwindow_size+a)

% --- Executes during object creation, after setting all properties.

function slider4_CreateFcn(hObject, eventdata, handles)

% hObject handle to slider4 (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles empty - handles not created until after all CreateFcns called

% Hint: slider controls usually have a light gray background.

if isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))

set(hObject,'BackgroundColor',[.9 .9 .9]);

end

What could be wrong here ?

What h.ax should be replaced with ?

and can i create a code for the slider with its function in a GUI mode ?

Rik
on 20 Feb 2019

handles.ax should be replaced by whatever the handle for your axes object is, likely handles.axes1. And again, you have put code in your callback that loads data. That is something you should put in the createFcn of your GUI (or is it called startFcn?). A callback should be treated as an interupt: as little work as possible should be done in them. A callback will trigger often, every 200 ms you spend on loading that mat introduces 200 ms of delay.

% --- Executes on slider movement.

function slider4_Callback(hObject, eventdata, handles)

a=get(handles.slider,'Value');

set(handles.ax,'XLim',[-0.5 0.5]*handles.xwindow_size+a)

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Answer by Yair Altman
on 17 Feb 2019

In your example, both val and x are not scalars. When you multiply vectors/matrices in Matlab using the * operator, Matlab uses linear algebra rules to multiply the data. This causes an error because the two variables do not match in their size as required by linear algebra multiplication rules (that the number of rows in one multiplicant is equal to the number of columns in the other).

What you probably wanted to do instead was to multiple each element of val by the corresponding element in x (assuming that they are both vectors of the same size) - this is done with element-wise multiplication (.*) :

y = ECGsignal.*x*a;

Hassan Bosha
on 18 Feb 2019

still same problem , i just need a code to move the slider on zooming

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## 4 Comments

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