Thread Subject: Matlab: symbolic, expand

Hello,

Can I "fully" expand an expression using matlab?

for a simple example:
       a = x * x + 2*x + 1
       b = y * y

       a11 = a * b
       b11 = a / b

       f = a11 + b11

How can I expand f to a expression containing only x and y?

Thanks in advance.

Ting

<tingxing@gmail.com> wrote in message
news:ec72399e-7ff2-48a8-9a88-1e287b665ae9@w8g2000prd.googlegroups.com...
> Hello,
>
> Can I "fully" expand an expression using matlab?
>
> for a simple example:
> a = x * x + 2*x + 1
> b = y * y
>
> a11 = a * b
> b11 = a / b
>
> f = a11 + b11
>
> How can I expand f to a expression containing only x and y?
>
> Thanks in advance.
>
> Ting

If you have Symbolic Math Toolbox and have defined x and y to be sym
objects, then f should be "expanded" automatically.

syms x y
a = x * x + 2*x + 1
b = y * y
a11 = a * b
b11 = a / b
f = a11 + b11

*snip intermediate output*

f =

(x^2+2*x+1)*y^2+(x^2+2*x+1)/y^2

 If you want that result to be expanded even further, use EXPAND.

--
Steve Lord
slord@mathworks.com

Really! Thanks.

I guess my previous failure is the result of some grammar errors
made during defining intermediate expressions.

Ting

>
> If you have Symbolic Math Toolbox and have defined x and y to be sym
> objects, then f should be "expanded" automatically.
>
> syms x y
> a = x * x + 2*x + 1
> b = y * y
> a11 = a * b
> b11 = a / b
> f = a11 + b11
>
> *snip intermediate output*
>
> f =
>
> (x^2+2*x+1)*y^2+(x^2+2*x+1)/y^2
>
> If you want that result to be expanded even further, use EXPAND.
>
> --
> Steve Lord
> sl...@mathworks.com