Thread Subject: symbolic to double transfer function.

Help needed!!!

I have a symbolic function based on symbolic variable 's' , for example:

f=1/(s+1)

f is a symbolic function of s.

Now I wanna manipulate f numerically, I do not know which command can help me:


when I use double(f) it gives out this error:

??? Error using ==> sym.double
DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.


Any help on how to convert it to double tranfer function is very appreciated...

Bets,
MS

On 9/19/2011 3:11 PM, Mohammad Salehizadeh wrote:
> Help needed!!!
>
> I have a symbolic function based on symbolic variable 's' , for example:
>
> f=1/(s+1)
>
> f is a symbolic function of s.
>
> Now I wanna manipulate f numerically, I do not know which command can help me:
>
>
> when I use double(f) it gives out this error:
>
> ??? Error using ==> sym.double
> DOUBLE cannot convert the input expression into a double array.
> If the input expression contains a symbolic variable, use the VPA function instead.
>
>
> Any help on how to convert it to double tranfer function is very appreciated...
>
> Bets,
> MS

try subs:

EDU>> syms s
EDU>> f=1/(1+s)
  
1/(s + 1)
  
EDU>> s=1
EDU>> subs(f)

     0.5000

EDU>> s=5
EDU>> subs(f)

     0.1667

--Nasser