I don't why I get error when i run this code In an assignment A(I) = B, the number of elements in B and I must be the same. " Error in prob5 (line 26) v(i+1)=vi+​(1/6)*(k11​+2*k21+2*k​31+k41);

%Script that demonstrates the Runge-Kutta integration for a first order problem
%the problem to be solved is:
%vprime= @(xi,ti) 0.5*ui-1.5*vi
%uprime=2*ui-(2/3)*u^.3-vi
h=0.1; %h is the time step.
u0=0;
v0=0;
ti=t0;
to=0;
vi=v0;
tf=10;
ui=u0;
n=tf-t0/tf;
%iterate
 for i=0:n
 vprime=@(vi,ui,ti) 0.5*ui-1.5*vi;
 uprime=@(vi,ui,ti)2*ui-(2/3)*u.^3-vi;
 k11=h*vprime(vi,ui,ti);
 k12=h*uprime(vi,ui,ti);
k21=h*vprime(vi+(1/2)*k11,ui+(1/2)*k12,ti+h/2);
k22=h*uprime(vi+(1/2)*k11,ui+(1/2)*k12,ti+(1/2)*h);
k31=h*vprime(vi+(1/2)*k21,ui+(1/2)*k22,ti+(1/2)*h);
k32=h*uprime(vi+(1/2)*k21,ui+(1/2)*k22,ti+(1/2)*h);
k41=h*vprime(vi+k31,ui+k32,ti+h);
k42=h*uprime(vi+k31,ui+k32,ti+h);
v(i+1)=vi+(1/6)*(k11+2*k21+2*k31+k41);
u(i+1)=ui+(1/6)*(k12+2*k22+2*k32+k42);

   end
  v(i+1)
  u(i+1)

[Matt Fig]

Please learn to format your code. Simply highlight the code, then hit the button that looks like {}Code

Answer 1

[Image Analyst]

Set a breakpoint on the line:

v(i+1)=vi+(1/6)*(k11+2*k21+2*k31+k41);

You'll see one of the variables vi or k11, k21, k31, or k41 is not a single number. You can't set one element of an array equal to an array (unless it's a special kind of array called a cell array). For example v(2) can't be [1 2 3 4 5] - that's too many numbers, it has to be just one number, like 42.