How to rotate a line on a center point?

Hi, given the center point is (1,1). How can I rotate a line with a radius of 0.8? And the line follows a right click of a mouse.The graph needs to be in a 2dimension. Thank you.

Answer 1

[Geoff Hayes]

Nik - if each right mouse-click corresponds to a single rotation (given a fixed rotation angle), then you can use the below code to rotate your line of radius r around the centre point (1,1).

 function rotatingLine

    close all;

    xo = 1;
    yo = 1;

    r = 0.8;
    n = 100;

    theta = pi/18; % 10 degree rotation angle

    coords = zeros(2,n);

    coords(1,:) = linspace(0,0,n);
    coords(2,:) = linspace(0,r,n);

    hPlot = plot(coords(1,:),coords(2,:));
    axis([-2*r 2*r -2*r 2*r]);
    axis('equal');
    axis('manual');

    set(gcf,'WindowButtonDownFcn',@onButtonDown);

    function onButtonDown(hObject,~)
        selectionType = get(hObject,'SelectionType');

        if strcmpi(selectionType,'alt')
           % right button click, so rotate line
           R = [cos(theta) -sin(theta) ; sin(theta) cos(theta)];
           coords = R*coords;
           set(hPlot,'XData',coords(1,:),'YData',coords(2,:));
        end
    end
 end

In the above example, we assume that the rotation angle is 10 degrees. An array of x and y coordinates is created so that the line is plotted pointing north from the origin of (1,1). We then use assign a callback to the current figure (gcf) WindowButtonDownFcn event. This callback checks to see if the selection type is alt (for a right-button click) and then we apply the rotation to the coordinates, rotating the line 10 degrees counter-clockwise about the origin. Each subsequent right-button click does the same.