getting function as an argument of function

hi, i am writing a matlab script that take function f which is a function of x and y and evaluate function f for some values of x and y. however i cannot get function, in my following code, f is seen as an array not a function. how can i get f. how can i evaluate at some points?

thanks.

function backEuler(f,x0,y0,h,N)
x(1)=x0;
y(1)=y0;
for i=1:N
  x(i+1)=x(i)+h;
  y_temp=y(i)+h*x(i)*x(i);
  y(i+1)=y(i)+h*f(x(i+1),y_new);
end
plot(x,y);

end

Answer 1

[Naz]

Let's say your function is f(x,y)=2x+y. You need to create this function prior you send it to your backEuler:

f=@(x,y)2*x+y;
backEuler(f,2,3,0,0);

The above lines go into the Command Window. Now, your backEuler function could be a separate file .m-function:

function backEuler(f,x0,y0,h,N)
x(1)=x0;
y(1)=y0;
for i=1:N
  x(i+1)=x(i)+h;
  y_temp=y(i)+h*x(i)*x(i);
  y(i+1)=y(i)+h*f(x(i+1),y_new);
end
plot(x,y);
end

Just file->new->function, paste the above script and save it as backEuler (make sure that matlab does not have the function with the same name). Also, to use this function you need to set matlab to a current folder. That's it.

[Naz]

You can also call your function this way:

backEuler(@(x,y)x+y,2,3,0,0);