It looks like you want to create function in a file and run it. Refere Create function in files for more information. Here is the code
function u = expand(x,t)
k = .15;
L = 50;
u0 = 100;
S = 0;
N= 50;
for n = 1:2:2*N+1
S = S + 1/n*exp((-n^2)*(pi^2)*k*t/(L^2))*sin((n*pi*x)/L);
end
u=(4*u0*S)/pi;
end
To plot you can run
a1 = expand(1:30,30);
a2 = expand(25,1:30);
plot(a1);
plot(a2);
from the command line or from another file.
