Displaying information about the data set by clicking on its plot and then show a value that is associated with the (x,y) point

Hello,

So, I have a GUI and I'll plot a figure in this GUI. Then I want the user to be able to click somewhere on the curve, and then the information about that point will show up. I followed what was said here: https://www.mathworks.com/matlabcentral/answers/11668-displaying-information-about-the-data-set-by-clicking-on-its-plot

But, also, I want, aside from showing the x and y coordinates, to show another information that's associated with each (x,y) point. Like a (x,y) point indicated the value of z. Is it possible?

For example:

x = 

    0.0960    0.2496    0.4032    0.5568    0.7104    0.8640    
    1         2         3         4         5         6    
    7         8         9         10        11        12         
    13        14        15        16        17        18     
    
 y = 
    
    0.0960    0.2496    0.4032    0.5568    0.7104    0.8640   
    19        20        21        22        23        24    
    25        26        27        28        29        30         
    31        32        33        34        35        36   
    
fh = figure;
plot(x(2,:), y(2,:)); hold on;
plot(x(3,:), y(3,:)); hold on;
plot(x(4,:), y(4,:)); hold on;

datacursormode on
dcm = datacursormode(gcf); 
set(dcm,'UpdateFcn',@myupdatefcn)

function txt = myupdatefcn(trash,event)
pos = get(event,'Position');
dts = get(event.Target,'Tag');  
txt = {dts,...
       ['x: ',num2str(pos(1))],...
     ['y:',  num2str(pos(2))]}; 
 

I want to show x(1, ?) and y(1, ?) when the user clicks on a point in the curve.

Thank you all

[Adam Danz]

Is the figure external to the GUI (I see you're producing a figure in your code).

If not, what kind of app are you building? AppDesigner? Guide? uicontrol?

[Pedro Augusto de Castro e Castro]

The figure is plotted in a GUI axes, once the user press a push button. I'm using GUIDE.

Answer 1

[Matt J]

....
set(dcm,'UpdateFcn',@(t,e) myupdatefcn(t,e,x,y) );

function txt = myupdatefcn(~,event,xdata,ydata)

    pos = get(event,'Position');
    dts = get(event.Target,'Tag'); 
    
    [~,j]= find( xdata==pos(1) & ydata==pos(2)  );

    txt = {dts,...
           ['x: ',num2str(pos(1)),'    x(1,?):  ', num2str(xdata(1,j))],...
           ['y: ',num2str(pos(2)),'    y(1,?):  ', num2str(ydata(1,j))]}; 
       
end

[Adam Danz]

@Pedro, in addition to these changes, you should also make the following changes.

1) Your code is creating a new figure rather than using your GUI axes. To fix that, specify the axes in all of the graphics functions. This is generally a good practice.

hold(handles.axes1, 'on')               % provide axis handle
plot(handles.axes1, x(2,:), y(2,:));	  % provide axis handle
plot(handles.axes1, x(3,:), y(3,:));    % provide axis handle
plot(handles.axes1, x(4,:), y(4,:));    % provide axis handle

datacursormode(handles.figure1,'on')    % provide figure handle
dcm = datacursormode(handles.figure1);  % provide figure handle
set(dcm,'UpdateFcn',@(t,e) myupdatefcn(t,e,x,y) );

2) In the update function, it is assumed that the additional information for each point is stored in the Tag property of each line object. Currently your tag properties are empty which will result in an empty line in your datatip window. So, you'll either need to assign a constant value to the tag property or you'll need to select some other bit of information to display.

% Example:
plot(handles.axes1, x(2,:), y(2,:),'Tag','line1')

[Pedro Augusto de Castro e Castro]

Thank you! This works!

@Adam, I plotted the figure using the GUI axes (I'm sorry about the example I've put in the question, it was not clear).

I've put the code inside the ButtonDownFcn related to the GUI axes in question. When I put the handle like this

datacursormode(handles.graph_5, 'on')

it gives me an error.

Thanks about the Tag property!

[Adam Danz]

That should give you an error. If you take a 2nd look at my code, I provided the figure handle to datacursormode, not an axes handle.

[Pedro Augusto de Castro e Castro]

I see. So what would be the figure handle? The GUI figure?

[Adam Danz]

For GUIDE GUIs, yes. It's not required, but recommended.

[Pedro Augusto de Castro e Castro]

Ok! It's done then. Now it works.

Thank you!