# getting function as an argument of function

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Ali Isik on 13 Nov 2011
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

Naz on 13 Nov 2011
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 on 13 Nov 2011
You can also call your function this way:
backEuler(@(x,y)x+y,2,3,0,0);