Animating the movement of a figure

I have written a code which makes makes a rectangle rotate about a certain point bya certain angle anticlockwise, but when I proceed on the animation, it draws every single rectangle as it is rotated. How can I make the rectangle rotate without leaving a trace after every iteration?

Here is the code which inolves some funtions:

function [colouredshape] = filledshape(shape,c)
% This function will draw a shape that is filled of a certain colour

fill(shape(1,:),shape(2,:),c);

end

%%%%%%%%%%%%%%%%%%%

function [finalshape] = rotateabout(shape,a,x,y)
% this function will rotate a shape anticlockwise about a certain point rather than the
% origin (angle a, coordinates (x,y))

[newshape] = translate(-x,-y,shape);

[rotatedshape] = rotate(newshape,a);

[finalshape] = translate(x,y,rotatedshape);


end

% This is animation

n = 10;
rectangle1 = [10 10 11 11 10; 1 5 5 1 1];

for a = linspace(0,pi/2,n)
    
    [finalshape] = rotateabout(rectangle1,a,10,5); 
    
filledshape(finalshape,'b')
 

drawnow
pause(0.1)
end

Answer 1

[Andreas Bernatzky]

A rough and quick example:

for(n=1:1:360)
    RectangleData = calcRectangle(n); %calculate your new position
    hRectangle = plot(RectangleData); % plot your rectangle
    % Now get rid of it.
    delete(hRectangle); %clear your plot
end

I can not test your code at the moment. But try the delete() after your pause()

Hope I could help

[Iñigo de la Joya]

The problem is that I cannot call a function any varibale which can then be deleted: when I use my function I have to write it by itself, not in the format A=funtion(...).

Nevertheless, if I did manage to call it a variable, at the end of the loop my last drawn figure would also be deleted and I want it to remain on the grid.

[Andreas Bernatzky]

Ok and if you include an if-clause for the delete-function?

if(currentIteration < maxIterations)
    delete(shape); % if you iterate 
end

Or you draw the last known position again after the last iteration? (After the for-loop)

[Andreas Bernatzky]

Thats my solution:

%% shapeRotor
% rotates shape around a rotation point
%% Andreas Bernatzky 15.12.2019
clear all;
close all;

figure(1)
shape = rand(2,100);
ShapeObj = fill(shape(1,:),shape(2,:),'b');
%% now draw your stuff
for(n=1:1:360)

    ShapeObj = rotateAround(1,0.5,0.5,ShapeObj.XData,ShapeObj.YData); % I will rotate around (0.5,0.5) dont know if that fits your usecase but does not matter
    ShapeObj = fill(ShapeObj.X,ShapeObj.Y,'b');
    xlim([0 1])
    ylim([0 1]);
    pause(0.05)
end
%-----------------------------------------------------------------------------
%% FUNCTIONS
%rotate your shape
% angle in degree
% centerX rotation X 
% centerY rotation Y
function newShape = rotateAround(angle,centerX,centerY,xData,yData)
    angle = angle * pi/180;
    rotatedX = cos(angle) * (xData - centerX) - sin(angle) * (yData-centerY) + centerX;
    rotatedY = sin(angle) * (xData - centerX) + cos(angle) * (yData -centerY) + centerY;
    newShape.X = rotatedX;
    newShape.Y = rotatedY;
end

[Iñigo de la Joya]

Sorry but this doesnt work when I run it on Matlab. It draws a very strange random pattern if you try it.

One question: when I use a function to for example draw a figure, how can I store it inside a variable so that I can then delete the figure?

[Andreas Bernatzky]

The strange pattern is normal because I use the rand() function.

you should see some blue and white shapes. (look at picture)

Maybe my example was a little bit confusing.

For your question:

FigureStorage = plot(someXvalues,someYvalues);
delete(FigureStorage);