MATLAB: Show mouse position in another subplot

copy mousemousemouse positionplotsubplot

I have a plot with two subplots, one frontal xray and one sagital xray, both with the same height, taken at the some moment. Hence y position in subplot 1 equals y position subplot 2.

I have to mark some points in subplot 1, but while moving my mouse in subplot 1, i want to show a (also moving) horizontal line in sublot 2, indicating the y value of the current mouse position from subplot 1. How can i make this?

Best Answer

You can use WindowButtonMotionFcn callback if figure. Run the following example

f = figure();
ax_up = subplot(2, 1, 1);
hold(ax_up);
ax_up.YLim = [0 2];
ax_down = subplot(2, 1, 2);
hold(ax_down);
ax_down.YLim = [0 2];
l = yline(0, 'r');
f.WindowButtonMotionFcn = @(fig, eve) btnCb(fig, eve, ax_up, l);
function btnCb(~, ~, ax_up, l_h)
    y = ax_up.CurrentPoint(1, 2);
    if (ax_up.YLim(1) < y) && (y < ax_up.YLim(2))
        l_h.Value = y;
    end
end

Related Solutions

MATLAB: Live line plotting over a surface/mesh/imagesc plot.

Here's a functional demo that uses the WindowButtonMotionFcn property of a figure to capture the mouse position which is used to detect the closest (x,y) coordinates to the mouse within the axes. It continually updates a set of crosshairs that display the coordinates and updates two subplots showing the values along the selected row and column.

See inline comments for details.

Create the data and set up the plot

% Create data
data = peaks(1000); 
% Plot data in main axis
ax(1) = subplot(4,1,[1,2]); 
imagesc(ax(1), data)
ax(1).YDir = 'Normal'; 
axis(ax(1),'equal')
axis(ax(1),'tight') %required!
ax(1).Parent.WindowState = 'Maximized';  % maximize figure
ax(1).Toolbar.Visible = 'off'; % otherwise, toolbar may hide axis title
xlabel(ax(1), 'x axis lable')
ylabel(ax(1), 'y axis lable')
title(ax(1), 'Data')
% Set up cross hairs at axis edges
gobj(1) = xline(min(xlim(ax(1))), 'k-');
gobj(2) = yline(min(ylim(ax(1))), 'k-');
% Set up subplot 2; do all formatting here
ax(2) = subplot(4,1,3); 
gobj(3) = plot(ax(2), 1:size(data,2), nan(1,size(data,2)), '-ko', 'MarkerSize', 4);
xlabel(ax(2), 'x index')
ylabel(ax(2), 'x value')
axis(ax(2), 'tight')
% Set up subplot 3; do all formatting here
ax(3) = subplot(4,1,4); 
gobj(4) =  plot(ax(3), 1:size(data,1), nan(1,size(data,1)), '-ko', 'MarkerSize', 4);
xlabel(ax(3), 'y index')
ylabel(ax(3), 'y value')
axis(ax(3), 'tight')
% After values are set above, assign windowbuttonmotion fcn
set(ax(1).Parent,'windowbuttonmotionfcn', {@mouseMove, data, ax, gobj});

Define the WindowButtonMotionFcn

function mouseMove(~, ~, data, ax, gobj)
% gobj(1) is xline
% gobj(2) is yline
% gobj(3) is subplot 2 line
% gobj(4) is subplot 3 line
% ax is a vector of subplot handles from top to bottom
% data is the imagesc data
% Get mouse coordinate, round to nearest integer.
C = ax(1).CurrentPoint;
x = round(C(1,1));
y = round(C(1,2));
% If mouse isn't on axis, do nothing.
if x < ax(1).XLim(1) || x > ax(1).XLim(2) || y < ax(1).YLim(1) || y > ax(1).YLim(2) 
    return
end
% Update crosshairs
gobj(1).Value = x; 
gobj(1).Label = x; 
gobj(2).Value = y; 
gobj(2).Label = y; 
% Update main title
% title(ax(1), sprintf('(x,y) = (%d, %d)', x, y)); 
% Update x-subplot
gobj(3).YData = data(x,:); 
title(ax(2), sprintf('X = %d', x))
% Update y-subplot
gobj(4).YData = data(:,y); 
title(ax(3), sprintf('Y = %d', y))
end

Addendum: turn on/off interactivity

Press the left mouse button to turn on interactivity and the right mouse button to pause it so that the crosshairs and subplots do not update with mouse motion.

%% Add this section to the first block of code where the figure is created.
% Remove the windowbuttonmotionfcn in that section. 
WindowButtonMotionFcnInput = {@mouseMove, data, ax, gobj}; 
set(ax(1).Parent,'windowbuttondownfcn', {@startStopMouseMove, WindowButtonMotionFcnInput})
%% This function responds to mouse clicks and either assigns 
% or removes the windowbuttonmotionfcn
function startStopMouseMove(hobj,~,WindowButtonMotionFcnInput)
buttonID = hobj.SelectionType; 
switch buttonID
    case 'normal'  %left mouse button
        % Start interactivity
        set(hobj,'windowbuttonmotionfcn', WindowButtonMotionFcnInput);
    case 'alt'     % right mouse button
        % Stop interactivity
        set(hobj,'windowbuttonmotionfcn', []);
end
end

MATLAB: Deletting X and Y axes ticks

set(gca,'xtick',[]) set(gca,'ytick',[])

Best Answer

Related Solutions

MATLAB: Live line plotting over a surface/mesh/imagesc plot.

MATLAB: Deletting X and Y axes ticks

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