How to fix this error?

This is the code:

 dx = .01 ; % Spacing of points on string
 dt =.001 ; % Size of time step

 c = 1 ;% Speed of wave propagation
 L = 0.64 ;% Length of string
stopTime = 30 ; % Time to run the simulation

 r = c*dt/dx ;
 n = L/dx+1
 k = 1
 h = 0.005
 d = 0.16

 % Set current and past to the graph of a plucked string
current = ((2*h*L^2)/(pi^2 * k^2 *d*(L-d)))*sin((k*pi*d)/L)*sin((k*pi*x)/L)*cos((c*k*pi*t)/L)
past = current ;
for t=0: dt : stopTime
 % Calculate the future position of the string
future ( 1 ) = 0 ;
 future ( 2 : n-1) = r^2*( current ( 1 : n-2)+current ( 3 : n ) ) + 2*(1-r^2)* current ( 2 : n-1) - past ( 2 : n-1);
future (n) = 0 ;

 % Set things up for the next time step
past = current ;
current = future ;

 % Plot the graph after every 10th frame
if mod( t /dt , 10) == 0
plot ( [ 0 : dx :L] , current )
axis ( [ 0 L -2 2 ] )
pause ( .001 )
end
end

The error at line 29 which is this one:

 ??? Error using ==> plot
 Vectors must be the same lengths.

 Error in ==> new at 29
 plot ( [ 0 : dx :L] , current )

How to fix the error?

Answer 1

[Peter Nave]

In the line

current = ((2*h*L^2)/(p ...

neither x nor t is defined.

Line:

if mod( t /dt , 10) == 0

testing for equality of two doubles is always dangerous.

[sing lai]

okay..thanks,do you know what actually the current means? current = ((2*h*L^)..., what is this equation should be put?