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How do i select a point on matlab UIaxes and then get data for it?

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I have a plot on UIAxes and i want to use the brush tool to select the already plotted data and get what points the user selects

Accepted Answer

Adam Danz
Adam Danz on 17 Feb 2020
Edited: Adam Danz on 28 Sep 2020
The brush tool is not (yet?) available on UIAxes as of r2019b; neither is rbbox. Update: the brush tool is now available as of r2020a.
Here's a workaround for releases <= r2019b.
The first block of code simulates an App by creating a plot on a UIAxes within a UIFigure.
The second block of code is a function that can be added to your App. When the function is called, the title of the axes will change to instructions for the user to draw a rectangle with their mouse. After drawing the rectangle, it will disappear and the (x,y) coordinates within or on the border of the rectangle will be returned.
See inline comments for details.
% Create a demo-app
app.myApp = uifigure();
app.UIAxes = uiaxes(app.myApp);
plot(app.UIAxes, rand(10,4),'o')
title(app.UIAxes, 'My Data')
% Call the custom function so the user can
% draw a temporary rectangle within the axes.
[x,y] = selectDatapoints(app.UIAxes);
function [x,y] = selectDatapoints(ax)
% Remove any pre-existing rectanlges (if any)
delete(findall(ax, 'Type', 'images.roi.Rectangle'))
% Get coordinates of all data points in the axes
xyobj = findall(ax.Children, '-Property','xData');
xydata = get(xyobj, {'XData','YData'});
xydataMat = cell2mat(xydata');
% change title of axes to instructions, in red
originalTitle = get(ax.Title, {'String', 'Color'});
set(ax.Title, 'String', 'Draw rectangle around desired datapoints', 'Color', 'r')
% allow user to draw rectangle; see more options:
pan(ax, 'off') %turn off panning so the interaction doesn't drag the data.
roi = drawrectangle(ax);
% quit if figure is closed
if ~isvalid(roi)
x = [];
y = [];
% Return original title
set(ax.Title, 'String', originalTitle{1}, 'Color', originalTitle{2})
% determine which coordinates are within the ROI
isIn = xydataMat(1,:) >= roi.Position(1) & xydataMat(1,:) <= sum(roi.Position([1,3])) ...
& xydataMat(2,:) >= roi.Position(2) & xydataMat(2,:) <= sum(roi.Position([2,4]));
% Delete ROI
% Return outputs
x = xydataMat(1,isIn);
y = xydataMat(2,isIn);

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More Answers (1)

Cameron B
Cameron B on 5 Jul 2020
Looks like there's something easier to do in 2020a. May want to try it out in 2019a or 2019b as I did not see it in the current documentation, but it seems to work fine for me.
%app.UIAxes will be our handle
x = 1:10; %some values for x
y = x*2; %some values for y
plot(app.UIAxes,x,y) %plot in the UIAxes
indx = app.UIAxes.Children(end).BrushData; %grab the indices
Priti Madurwar
Priti Madurwar on 26 Oct 2020
How do we get thos values back in command window?
bcz indx returns empty when called in command window.
how do i get those accurate values if i neeed to display them in some other window?

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