Re: Here is a dem of how to use the symbolic pkg. for derivatives of anonymous functions

[Oliver Heimlich]

On 29.06.2015 02:32, Doug Stewart wrote:
> It also demos Newton-Raphson roots.

Doug,

thanks for pointing me to this feature of the symbolic package. Did you 
know the “interval Newton method”? It computes enclosures of /all/ zeros 
of a function in a given domain and is globally convergent.

I have implemented it in the interval package and it can make great use 
of this particular feature to compute a derivative.

Oliver


% this is just a formula to start with
% have fun and change it if you want to.
f=@(x) x.^2 +3*x-1 + 5*x.*sin(x);

% the nex2 line take the Anonymous function into a symbolic formula
syms x;
ff=formula(f(x));
% now calculate the derivative of the function
ffd=diff(ff);
% and convert it back to an Anonymous function
df=function_handle(ffd)

fzero (f, infsup (-15, 10), df)

ans ⊂ 4×1 interval vector

    [-5.743488743719015, -5.743488743719013]
    [-3.0962279604822407, -3.09622796048224]
   [-0.777688831121563, -0.7776888311215626]
   [0.22911205809043574, 0.2291120580904359]