Slider Code problem with axes

Question

Hassan Bosha 2019-2-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445308-slider-code-problem-with-axes

评论： Rik 2019-2-20

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 ?

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Rik 2019-2-18

If you want to scroll through your data, why don't you use the Value property of the slider to change the XLim property of your axes object?

Hassan Bosha 2019-2-19

can you show me a example code for it ?

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Answer 1

Rik 2019-2-19

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445308-slider-code-problem-with-axes#answer_361690

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

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Rik 2019-2-19

The way to find out is trying it, but that looks like it should work.

You shouldn't load data from the disk inside a callback function. If you need data, use the guidata struct. Make sure you create the plot outside of the callback and then only change the bare minimum inside the callback. In this case you only need the last 3 lines, as the rest is unused.

If my answer worked for you, please mark it as accepted answer. It will help others with a similar question to find a working solution.

Also, I would discourage the use of GUIDE. It generates code that is bloated and hard to debug, as well as preventing you from using the full potential of programatic creation by all but forcing you to use a .fig file for your GUI.

My small guide to avoid GUIDE:

Make a figure (with f=figure;) and look into the doc for figure which properties you want to turn off (you probably want to set Menu and Toolbar to 'none')
Create buttons and axes and everything you need with functions like uicontrol and axes. Save the handles to each element to fields of a struct (like handles.mybutton=uicontrol(___);)
When you've finished loading all data (and saving it to fields of your handles struct), and creating all the buttons, save your handles struct to the guidata of your figure like this guidata(handles.f,handles);. (You can also use getappdata and setappdata)
You can set the Callback property of many objects. If you do, use a function name with an @ in front, or a char array that can be evaluated to valid code. (like @MyFunction or 'disp(''you pushed the button'')')
Callback functions will be called with two arguments: the first is a handle to the callback object, the second is eventdata that may contain special information. To get access to your data, just use handles=guidata(gcbo);. You can replace the gcbo function with the name of the first input to your callback function if you prefer.
More information about callbacks can be found in multiple places in the doc, for example here.

Hassan Bosha 2019-2-19

编辑：Hassan Bosha 2019-2-19

% --- 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 2019-2-20

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 2

Yair Altman 2019-2-17

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/445308-slider-code-problem-with-axes#answer_361398

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;