Heat equation using Boundary condition

 function [b,c] = eql (x,t,u,dudx)
 C=1; b=dudx; s=0;
 end
 function value = initial (x)
 value=2*x / (1+x^2)
 end
 function [pl,ql, pr,qr]= ba(xl,ul,xr,ur,t)
 pl=ul; ql=0; pr=ur-1; qr=0;
 end
u=pdepe(0,@eql,@initial,@ba,x,t)

This statement is not inside any function.
(It follows the END that terminates the definition of the function "ba".)

 x=linspace(0,1,20);
 t=linespace(0,2,10);
 surf(x,t,u)
 title('Surface plot of solution')
 xlabel('Distance X')
 ylabel('time T')
 zlabel('z axis')
 grid on
 

I ma unable to understand the error. Please help me to understand and rectify the error...

Answer 1

[Alan Stevens]

function statements of this form (i.e. functions eq1, initial and ba) need to go at the end of the script, not the start.

Answer 2

[Torsten]

 x=linspace(0,1,20);
 t=linspace(0,2,10);
 u=pdepe(0,@eql,@initial,@ba,x,t);
 surf(x,t,u)
 title('Surface plot of solution')
 xlabel('Distance X')
 ylabel('time T')
 zlabel('z axis')
 grid on

function [c,f,s] = eql (x,t,u,dudx)
 c=1; f=dudx; s=0;
 end
 function value = initial (x)
 value=2*x / (1+x^2);
 end
 function [pl,ql, pr,qr]= ba(xl,ul,xr,ur,t)
 pl=ul; ql=0; pr=ur-1; qr=0;
 end