# Using mouse for control in Matlab

So, it basically boils down to an old problem: how do I get some user-controlled inputs in Matlab?

Keyboard handling in real-time is basically nonexistant, joystick is alright, but the most easy way to get some input and freedom of controlling things is – to poll the mouse position.

Spoiler alert:

xy = get( 0, 'PointerLocation' )

Ok, so everything inside windows in Matlab has a parent-children relationship. Figure 21 contains an axis, axis contains a couple of plots, and so on. But above all those figures there is one root node – the screen itself. You can get the properties of the screen (including the current resolution) as:

get(0)

and among that there is a property that holds ‘PointerLocation’, so the x-y coords of the mouse pointer. To get it:

mouse = get( 0, 'PointerLocation' ) x = mouse(1) y = mouse(2)

Now for some usage – you can use it in any script that is running in Matlab, for example:

figure( 21 ) axis hold on while(1) mouse = get( 0, 'PointerLocation' ) plot( mouse(1), mouse(2), '.' ) pause( 0.01 ) end

The result? A trace of the mouse path.

Ok, something a little bit more ambitious – a simple cart with a reference position grabbed from mouse:

function some_silly_name_for_a_file t = 0:0.01:30; x = [5;0]; figure(1) for i=1:length(t) dx = cart( t(i), x ); x = x + dx*0.01; plot( x(1), 0, 'o' ) % I assume your screen resolution is 1920 axis( [0 1920 -1 1] ) pause( 0.01 ) end function dx = cart( t, x ) mouse = get( 0, 'PointerLocation' ); xr = mouse( 1 ); u = 2*(xr-x(1)); dx = [ x(2); -x(2)+u ]