MATLAB: Can I use arrows to move Data Tips on scatter plots

data tipMATLABscatter

I know that when using the plot function with data tips you can use the arrow keys to move the data tip through the data set. Is there a way to do this with scatter plots as well? I need to be able to define the marker color individually, which is why I'm using scatter instead of plot.

Best Answer

Hi David,

Edit: I have updated the code and it works. It's better if the callback is on KeyPressFcn, especially for plots with many points.

I have taken part of code from Adam's answer, thanks Adam!

% clear functions % On the second run, datatip will continue from where it stopped the previous run, if you mind that, uncomment this line
fig = figure('KeyPressFcn', @ArrowKeyPressed);
ax = axes(fig);
x = linspace(0,2*pi,25);
y = cos(x) + rand(1,numel(x))/2;
sz = (abs(sin(x))*4+1)*25;
c = linspace(1,10,numel(x));
scatter(ax, x,y,sz,c,'filled','MarkerEdgeColor', 'k');
grid on

It is possible to write a callback for the figure that would detect arrow key presses

function ArrowKeyPressed(Source, Event) 
    persistent dtNum 
    if isempty(dtNum) % Initialise the variable
        dtNum = 0;
    end
    
    % Get axes handle
    ax = findall(Source, 'Type', 'axes');
    % Get the scatter object
    h = findall(ax, 'Type', 'scatter');
    % Get the datatips associated with scatter object
    datatipObjs = findobj(h,'Tag','datatip');
    % Get the number of points
    numPoints = length(h.XData); % assuming x is a vector
    
    % Setting up the counter
    switch Event.Key
        case 'leftarrow'
            if dtNum > 1
                dtNum = dtNum - 1;
            else
                dtNum = 1;
            end
        case 'rightarrow'
            if ~isequal(dtNum, numPoints)
                dtNum = dtNum + 1;
            end
        otherwise
            return
    end
    
    % Removing the previous (all if there are more) and creating the next datatip
    if isvalid(datatipObjs); delete(datatipObjs); end
    datatip(h, h.XData(dtNum), h.YData(dtNum));
end

Related Solutions

MATLAB: No data tip interaction when adding a second axis

ax2 is blocking ax1. The datatip on ax2 works fine but there are no data in ax2 so you're not seeing any datatips.

Solution: Put ax2 on the bottom:

uistack(ax2, 'bottom')

If you plan on plotting anything on ax2, you'll need to make ax1 color = none so you can see ax2 (and you won't need to set ax2 color to none).

MATLAB: How to use uipushtool to click and drag plots in figure

Miles - ok, when I push the button, I see a slightly different error

 Error using interactive_move>dragger (line 80)
 Not enough input arguments.

Look closely at the dragger function signature

 function dragger(~,~,type)

It is expecting three input parameters. The first two are typically the source handle and some event data. But the third, in this case, appears to be a custom parameter which you need to define when you add dragger as the callback to the uipushtool

 p = uipushtool(h,'CData',b,'TooltipString','Drag Plot',...
        'Separator','on','ClickedCallback',@dragger);

Note how the other callbacks do this

 set(gcf, 'windowbuttondownfcn', {@dragger,1});
 set(gcf, 'windowbuttonmotionfcn', {@dragger,2});
 set(gcf, 'windowbuttonupfcn', {@dragger,3});
 set(gcf, 'keypressfcn', {@dragger,4});

So you need to pass in a "type" parameter.

But I don't know if this will fix your problem which is that you only want to drag plots when the button is clicked. I think that the callback for this tool should be something more like

function enableDragger(~,~)
if isempty(get(gcf, 'windowbuttondownfcn'))
    set(gcf, 'windowbuttondownfcn', {@dragger,1});
    set(gcf, 'windowbuttonmotionfcn', {@dragger,2});
    set(gcf, 'windowbuttonupfcn', {@dragger,3});
    set(gcf, 'keypressfcn', {@dragger,4});
else
    set(gcf, 'windowbuttondownfcn', []);
    set(gcf, 'windowbuttonmotionfcn', []);
    set(gcf, 'windowbuttonupfcn', []);
    set(gcf, 'keypressfcn', []);
end

So you add (or remove) the dragger function to (or from) the above callbacks. The only time that you can drag is when you've pressed the button (I'm assuming that the only code you have to add dragger as a callback to the four functions is through the enableDragger function) and that when you press the button again, you won't be able to drag.

Best Answer

Related Solutions

MATLAB: No data tip interaction when adding a second axis

MATLAB: How to use uipushtool to click and drag plots in figure

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