Set data tips programmatically?

Question

I need to be able to set data tips programmatically from a list of array of x axis values. For example, I create a figure and plot my data.

figure;plot(t1,[filter(b,a,Gyro(:,2)),filter(b,a,Gyro(:,4))])

I have a set of timestamp values from t1 variable (time) (e.g. [0.450, 0.854, 1.2343....]) where I want to place data tips to mark certain events in my data. Without having to place them every time manual by clicking and saving data trip... How can I pass them as array and do this programmatically through matlab script?

Solution

You can add matlab datatip programatically and customize them to an extent.

The function below shows how to add a few datatip, position them and customize their display:

The code for this demo (save that in a file demo_datatip.m and run it to obtain the above figure) :

function h = demo_datatip

    %// basic sample curve
    npts = 600 ;
    x = linspace(0,4*pi,npts) ;
    y = sin(x) ;

    %// plot
    h.fig = figure ;
    h.ax = axes ;
    h.plot = plot(x,y) ;

    %// simulate some event times
    time_events = x([25 265 442]) ; %// events type 1 at index 25, 265 and 422

    %// define the target line for the new datatip
    hTarget = handle(h.plot);

    %// Add the datatip array
    h.dtip = add_datatips( time_events , hTarget ) ;


function hdtip = add_datatips( evt_times , hTarget )
    %// retrieve the datacursor manager
    cursorMode = datacursormode(gcf);
    set(cursorMode, 'UpdateFcn',@customDatatipFunction, 'NewDataCursorOnClick',false);

    xdata = get(hTarget,'XData') ;
    ydata = get(hTarget,'YData') ;

    %// add the datatip for each event
    for idt = 1:numel(evt_times)
        hdtip(idt) = cursorMode.createDatatip(hTarget) ;
        set(hdtip(idt), 'MarkerSize',5, 'MarkerFaceColor','none', ...
                  'MarkerEdgeColor','r', 'Marker','o', 'HitTest','off');

        %// move it into the right place
        idx = find( xdata == evt_times(idt) ) ;%// find the index of the corresponding time
        pos = [xdata(idx) , ydata(idx) ,1 ];
        update(hdtip(idt), pos);
    end

function output_txt = customDatatipFunction(~,evt)
    pos = get(evt,'Position');
    idx = get(evt,'DataIndex');
    output_txt = { ...
        '*** !! Event !! ***' , ...
        ['at Time : '  num2str(pos(1),4)] ...
        ['Value: '   , num2str(pos(2),8)] ...
        ['Data index: ',num2str(idx)] ...
                };

If you need to delete a data tip, you can simply call delete(datatip_handle) on it's handle (or even an array of handles to delete them in group).

Comments

[evolved]

In Matlab R2015b I get the error Undefined function 'update' for input arguments of type 'matlab.graphics.shape.internal.PointDataTip'. Do you know how to solve this issue?

[evolved]

I think I found a solution. Using set(hdtip(idt), 'Position', pos) followed by updateDataCursors(cursorMode) instead of update(hdtip(idt), pos) worked for me.

[Hoki]

@evolved, thanks for the info. My example was written for older MATLAB versions, your addition will help users of the current versions.