Invalid expression...Line 16 column 48

function [x ,t,DR, DT]=homogeneous(N,dt,x0,R,T,eta,V,W)
   kB=1.38e-23;
   gamma=6*pi*R*eta;
   DT=kB*T/gamma;
   DR=6*DT/(8*R^2); x(1,:)=x0;
   theta=0;
 
 for n=1:1:N
     x(n+1,:)=x(n,:)+sqrt(2*DT*dt)*randn(1,2);
     theta=theta+sqrt(2*DR*dt)*randn(1,1);
     theta=theta+dt*W;
     x(n+1,:)=x(n+1,:) + dt*V*[cos(theta) sin(theta)];
     
     cla
     hold on
     plot(x(1:n+1,1)) * 1e6;x(1:n+1,2)*1e6; 'k')
     plot(x(n+1,1))*1e6;x(n+1,2)*1e6; 'o';...
      'MarkerEdgeColor' ; 'k'; ...
      'MarkerEdgeColor' ;'g')

     hold off
     axis equal square
     title(['velocity= ' num2str(V*1e6) '\mum/s,' , ...
               'angular velocity= ' num2str(W) 'rad/s,' , ...
               'time= ', num2str(dt*(n+1)) 's'])
     xlabel('x[\mum]')
     ylabel('y[\mum]')
     box on 
     axis equal
     drawnow();
 end
 
 t=[0:dt:(N-1)*dt];

Answer 1

[Rik]

You have a closing parenthesis too early:

plot(x(n+1,1))*1e6;x(n+1,2)*1e6
%            ^

Also, you should use commas to separate arguments instead of semicolons.

Additionally, it does not make sense to use cla inside the loop. If you want to show only 1 plot, you should update the XData property instead of clearing the axes. You should also move the calls to title etc to outside the loop.

[Rik]

I think you may benefit from a crash course on using Matlab. None of what you wrote in that comment will work as intended.

If you have a 'not enough input arguments' error, you either need to provide the input arguments, or provide default values (use the nargin function, or use the exist function to determine if an input was provided).

[Walter Roberson]

Is this possibly intended for use in simscape ?

Notice that the line

W= +|- 3.14 rad 1/s .

is the only one where you use = and the only one where you do not use []

[ilke]

function [x ,t,DR, DT]= Usfntitled(N,dt,x0,R,T,eta,V,W)
 kB=1.38e-23;
 gamma=6*pi*R*eta;
 DT=kB*T/gamma;
 DR=6*DT/(8*R^2);
 
 x(1,:)=x0;
 theta=0; 

for n=1:1:N
     x(n+1,:)=x(n,:)+sqrt(2*DT*dt)*randn(1,2);
     theta=theta+sqrt(2*DR*dt)*randn(1,1);
     theta=theta+dt*W;
     x(n+1,:)=x(n+1,:) + dt*V*[cos(theta) sin(theta)];
     
     cla
     hold on
     plot(x(1:n+1,1)*1e6,x(1:n+1,2)*1e6, 'k')
     plot(x(n+1,1)*1e6,x(n+1,2)*1e6, 'o',...
      'MarkerEdgeColor' , 'k', ...
      'MarkerEdgeColor', 'g')

        hold off
        axis equal square
        title(['velocity= ' num2str(V*1e6) '\mum/s,' , ...
               'angular velocity= ' num2str(W) 'rad/s,' , ...
               'time= ', num2str(dt*(n+1)) 's'])
        xlabel('x[\mum]')
        ylabel('y[\mum]')
        box on 
        axis equal
        drawnow();
end
t=0:dt:(N-1)*dt;

[ilke]

"Additionally, it does not make sense to use cla inside the loop. If you want to show only 1 plot, you should update the XData property instead of clearing the axes. You should also move the calls to title etc to outside the loop" I couldn't do this one.But ,this code must be true but ı dont see any plot. I was hoping you might be able to help me with.

[Rik]

Have you tried using the debugger to go through your code step by step? I don't have access to Matlab right now and you did not mention plausible inputs, so I can't test your code.

[Walter Roberson]

function [x ,t,DR, DT]= Usfntitled(N,dt,x0,R,T,eta,V,W)
 kB=1.38e-23;
 gamma=6*pi*R*eta;
 DT=kB*T/gamma;
 DR=6*DT/(8*R^2);
 
 x(1,:)=x0;
 theta=0;
 ax = gca;
 cla(ax);

for n=1:1:N
     x(n+1,:)=x(n,:)+sqrt(2*DT*dt)*randn(1,2);
     theta=theta+sqrt(2*DR*dt)*randn(1,1);
     theta=theta+dt*W;
     x(n+1,:)=x(n+1,:) + dt*V*[cos(theta) sin(theta)];
     
     if n == 1
         hold(ax, 'on')

        h1 = plot(x(1:n+1,1)*1e6,x(1:n+1,2)*1e6, 'k');
        h2 = plot(x(n+1,1)*1e6,x(n+1,2)*1e6, 'o',...
                  'MarkerEdgeColor' , 'k', ...
                  'MarkerEdgeColor', 'g')
        hold(ax, 'off')

        xlabel(ax, 'x[\mum]')
        ylabel(ax, 'y[\mum]')
        box(ax, 'on') 
     else
        set(h1, 'XData', x(1:n+1,1)*1e6, 'YData', x(1:n+1,2)*1e6);
        set(h2, 'XData', x(n+1,1)*1e6, 'YData', x(n+1,2)*1e6);
     end
     title(ax, ['velocity= ' num2str(V*1e6) '\mum/s,' , ...
               'angular velocity= ' num2str(W) 'rad/s,' , ...
               'time= ', num2str(dt*(n+1)) 's'])
     axis(ax,'equal','square')

     drawnow();
end

t=0:dt:(N-1)*dt;

[ilke]

Thank you,I appreciated for your help.I will try to apply your suggestions.