How can i replace the value of A(x) in the function defined in "f1"...

L=10;

a=0;

h=0.5;

n=20;

x=a:h:n;

%

f1=@(x,u) u * A(x);

%%% Initial Conditions %%%

u(1)=1;

for i=1:length(x)-1;

m1=h*f1(x(i), u(i));

m2=h*f1(x(i)+0.5*h, u(i)+0.5*m1);

m3=h*f1(x(i)+0.5*h, u(i)+0.5*m2);

m4=h*f1(x(i)+h, u(i)+m3);

u(i+1)=u(i)+(1/6)*(m1+2*m2+2*m3+m4);

end

plot(x,u,'k')

Answer 1

[M]

You can have a look here to know how to create if / else conditions:

https://mathworks.com/help/matlab/ref/if.html

Then you should not create A(x) = ... but A = ... and then access the element of A using A(i).

Answer 2

[Ameer Hamza]

Farooq, as already explained in response to your comment here: https://www.mathworks.com/matlabcentral/answers/517280-how-can-i-plot-this-graph you can define it as an anonymous function like this

A = @(x) (0<x & x<L).*(1+0.5*(1-cos(2*pi*x/L))-1/2) + (L<x).*1;
f1=@(x,u) u * A(x);