How can I get DataCursor information from stackedPlot on ButtonDown callback function?

Hi,

I am using StackedPlot in order to represent a set of values. What is interesting with the stackedPlot, is giving you with dataCursor over a location to display y-values for each plot.

My goal is to recover theese information (x-value and y-yvalues) by a double click interaction with the figure that containing my StackedPlot

I am able to use callback function windowButtonDown and to know if I am into my stackedPlot. My problem is that I am not able to obtain position and datacursor y-values information. Can you help me with this ?

Many thanks

Julien

Answer 1

[Adam Danz]

This solution uses undocumented methods of obtaining the data tip lables (see inline comments). As with all undocumented approaches, things can change in future releases. When the user clicks on a stackedplot the datacursor values and the x value will appear in the command window along with the associated axis labels. You can easily print the value to a file instead. Note that callback functions do not return outputs.

See footnotes for important details.

% Create statckedplot
fig = figure();
x = linspace(-5*pi, 5*pi, 500)'; 
y = [sin(2*x), sin(x), sin(.5*x), sin(.2*x), -sin(.1*x)];
sph = stackedplot(y,'XData',x,'DisplayLabels',["A","B","C","D","E"]);

% Assign callback function when user clicks on figure
fig.WindowButtonDownFcn = {@myFunc, sph};


function myFunc(~,~,sph)
% sph is the stackedplot handle. 
pause(0.5) % See footnote [1]

% Avoid seeing warning associated with undocumented methods
origState = warning('query', 'MATLAB:structOnObject');
cleanup = onCleanup(@()warning(origState));
warning('off','MATLAB:structOnObject')
S = struct(sph);            % Undocumented
Sdc = struct(S.DataCursor); % Undocumented

% Get data tip values
dataTipLabels = Sdc.DatatipLabels;
dataTipStr = get([dataTipLabels{:}],'String');
axLabels = sph.DisplayLabels;
   
% If the vertical CursorLine is not visible (ie, the mouse is not in the axes) or
% if the data tips are all NaN (sometimes this happens on the first click only) 
% then do nothing.  Otherwise, print the data tip values and axis labels to command
% window.
if strcmpi(Sdc.CursorLine.Visible,'off') || all(cellfun('isempty',dataTipStr(1:end-1)))
    return
else
    yDataStr = compose('   %s = %.3g', string(axLabels), string(dataTipStr(1:end-1)));
    fprintf('\nAt x = %s\n%s\n',dataTipStr{end},strjoin(yDataStr,newline))
end
end

%% Footnotes
% [1] The pause(0.5) is needed to give time for the data tip values to 
%   update. Notice that the line must remain still for a brief period
%   before the datatips appear.  In that time, the datatip values from
%   the previous datatip appearance are stored and we must wait for them
%   to regenerate before returning the updated value.  This lag is a 
%   property of the stackedplot data cursor:  Sdc.LingerTime. 

[julien gilles]

Hi Adam,

It works perfectly. Exactly what I was looking for.

Thank you very much.

Julien

[Adam Danz]

Glad I could help. If you need more precision on the printed values, change the "%.3g" part.

[julien gilles]

Thanks, but I am not interested in printed values.

What I really want is to recover the x value.

Then I find into my StackedLineChart.SourceTable the only line where x value appears (time column).

When I have got it, I write into a csv file my StackedLineChart.SourceTable line with all values. Because I am not showing all values into my Stackedplot, in fact I reduce the visible values of my stackedPlot with stackedPlot option.

[Adam Danz]

I see. So you're retrieving the x value, finding its index in your input x-data (with tolerance if it's floating pt decimal), and then using the index value to retrieve the y-values from the input table stored in the stacked line obj. Sounds like a good plan.