can I compare the previous state with current state in " While loop " ?

While loop used to move the ponts from position to position in one shot (each one second). now my question can I can iterate the while loop and

compare the past step with currenct step, for example If we want to calculate the X inside the while loop, we should compare X(i) with X(i-1) ?

Thanks in advance

    npts=1;center=[0 0];radius=1000;
    npts2=1;center2=[0 0];radius2=1000;
    % Initial direction/velocity of the points
    velocity = 28.8/3.6;
    velocity2 = 28.8/3.6;
    theta = rand(npts, 1) * 2*pi;
    g = 0.5 * radius + 0.5 * radius * rand(npts,1); 
    X_x=center(1)+g.*cos(theta);
    Y_y=center(2)+g.*sin(theta);
    XY = [X_x ,Y_y];
    
    theta2 = rand(npts2, 1) * 2*pi;
    g2 = 0.5 * radius2 + 0.5 * radius2 * rand(npts2,1); 
    X_x2=center2(1)+g2.*cos(theta2);
    Y_y2=center2(2)+g.*sin(theta2);
    XY2 = [X_x2 ,Y_y2];

    hfig = figure('Color', 'w');
    hax = axes('Parent', hfig);
    
    hdots(1) = plot(XY(1,1),XY(1,2),'Parent', hax,'Marker', '.','Color', 'k','LineStyle', 'none','MarkerSize', 10);
    hold(hax, 'on')
    axis(hax, 'equal')
 
    hdots(2) = plot(XY2(1,1),XY2(1,2),'Parent', hax,'Marker', '.','Color', 'r','LineStyle', 'none','MarkerSize', 10);
    hold(hax, 'on')
    axis(hax, 'equal')
    
    % Plot the circl e as a reference
    t = linspace(0, 2*pi, 100);
    plot(radius * cos(t) + center(1),radius * sin(t) + center(2))
    
    while all(ishghandle(hdots))  %Timestep=1:1:Totaltime 
    direction2 = rand(npts, 1) * 2 *pi;
       direction = rand(npts, 1) * 2 *pi;

    [XY2, direction2] = step(XY2, direction2, velocity2, radius2, center2);
    % Plot the dots as black markers
    [XY, direction] = step(XY, direction, velocity, radius, center);

    % Update the dot plot to reflect n ew locations
    set(hdots(2), 'XData', XY2(1,1), 'YData', XY2(1,2))
    set(hdots(1), 'XData', XY(1,1), 'YData', XY(1,2))

    % Force a r edraw 
    drawnow
    %pause (1)
   end 

Answer 1

[Voss]

X_current = 1;
X_previous = 0;
while true
    fprintf('current = %4.2f, previous = %4.2f\n',X_current,X_previous);
    if abs(X_current-X_previous) < 0.1
        fprintf('close enough\n');
        break
    end
    X_previous = X_current;
    X_current = X_previous + rand();
end

current = 1.00, previous = 0.00
current = 1.23, previous = 1.00
current = 1.71, previous = 1.23
current = 2.52, previous = 1.71
current = 3.25, previous = 2.52
current = 3.94, previous = 3.25
current = 4.33, previous = 3.94
current = 5.13, previous = 4.33
current = 5.65, previous = 5.13
current = 5.79, previous = 5.65
current = 5.80, previous = 5.79

close enough

[omar th]

First, thank you so much for your reponse. Regards to my code " while all(ishghandle) " used to move the random points each one second as one shot. Now, can I compare sigdB (line 37) for current step with sigdB for the previous step ?

Thanks in advance.

    npts=1;center=[0 0];radius=1000;
    npts2=1;center2=[0 0];radius2=1000;
    % Initial direction/velocity of the points
    velocity = 45/3.6;
    velocity2 = 45/3.6;
    theta = rand(npts, 1) * 2*pi;
    g = 0.5 * radius + 0.5 * radius * rand(npts,1); 
    X_x=center(1)+g.*cos(theta);
    Y_y=center(2)+g.*sin(theta);
    XY = [X_x ,Y_y];
    
    theta2 = rand(npts2, 1) * 2*pi;
    g2 = 0.5 * radius2 + 0.5 * radius2 * rand(npts2,1); 
    X_x2=center2(1)+g2.*cos(theta2);
    Y_y2=center2(2)+g.*sin(theta2);
    XY2 = [X_x2 ,Y_y2];

    hfig = figure('Color', 'w');
    hax = axes('Parent', hfig);
    
    hdots(1) = plot(XY(1,1),XY(1,2),'Parent', hax,'Marker', '.','Color', 'k','LineStyle', 'none','MarkerSize', 10);
    hold(hax, 'on')
    axis(hax, 'equal')
 
    hdots(2) = plot(XY2(1,1),XY2(1,2),'Parent', hax,'Marker', '.','Color', 'r','LineStyle', 'none','MarkerSize', 10);
    hold(hax, 'on')
    axis(hax, 'equal')
    
    % Plot the circl e as a reference
    t = linspace(0, 2*pi, 100);
    plot(radius * cos(t) + center(1),radius * sin(t) + center(2))
    
    while all(ishghandle(hdots))  %Timestep=1:1:Totaltime 
   distPoints = pdist2(XY,XY2,'euclidean')
        
   sig=sum(power*(distPoints).^-2);
   sigdB=10*log(sig) 
    direction2 = rand(npts, 1) * 2 *pi;
       direction = rand(npts, 1) * 2 *pi;

    [XY2, direction2] = step(XY2, direction2, velocity2, radius2, center2);
    % Plot the dots as black markers
    [XY, direction] = step(XY, direction, velocity, radius, center);

    % Update the dot plot to reflect n ew locations
    set(hdots(2), 'XData', XY2(1,1), 'YData', XY2(1,2))
    set(hdots(1), 'XData', XY(1,1), 'YData', XY(1,2))

    % Force a r edraw 
    drawnow
    pause (1)
   end 

[Voss]

% ... 
% your code
% ...

sigdB = NaN; % choose an appropriate initial value for sigdB

while all(ishghandle(hdots))
   
   sigdB_previous = sigdB;
   
   distPoints = pdist2(XY,XY2,'euclidean')
   sig=sum(power*(distPoints).^-2);
   sigdB=10*log(sig) 
   
   
   if isequal(sigdB,sigdB_previous) % Choose an appropriate comparison
                                    % and take appropriate action.
   end                              % Maybe the comparison should be somewhere 
                                    % else in the loop - I don't know.
   
   % ... 
   % your code
   % ...
   
end