# Heat equation using Boundary condition

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MOHIT SWADIA on 9 Oct 2023
Answered: Torsten on 9 Oct 2023
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...

Alan Stevens on 9 Oct 2023
function statements of this form (i.e. functions eq1, initial and ba) need to go at the end of the script, not the start.

Torsten on 9 Oct 2023
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