Maybe this?
sage: V = VectorSpace(SR, 2)
sage: x,y = var('x,y')
sage: f = V([x+y,x-x*y])
sage: f(2,3)
(5, -4)
On Thu, Feb 12, 2009 at 5:34 PM, Jason Grout
<jason-s...@creativetrax.com> wrote:
>
> What is the best way to deal with symbolic functions from R^n to R^m? A
> symbolic vector? Note some of the following ways that do not work. I'm
> not sure how I would specify that a given function f: R^2->R^2, for
> example, had input variables x and y (if, say, I wanted to define it
> f(x,y)=vector([x-y+c, x+2*c]) )
>
>
>
> sage: var('x,y')
> (x, y)
> sage: f(x,y)=(x+y,x-2*y)
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call last)
>
> /home/grout/.sage/temp/good/18016/_home_grout__sage_init_sage_0.py in
> <module>()
>
> /home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/all.pyc
> in symbolic_expression(x)
> 73 if isinstance(x, Expression):
> 74 return x
> ---> 75 return SR(x)
> 76
> 77 import desolvers
>
> /home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.pyc
> in __call__(self, x)
> 452 msg, s, pos = err.args
> 453 raise TypeError, "%s: %s !!! %s" % (msg,
> s[:pos], s[pos:])
> --> 454 return self._coerce_impl(x)
> 455
> 456 def _coerce_impl(self, x):
>
> /home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.pyc
> in _coerce_impl(self, x)
> 513 return self(x._sage_())
> 514 else:
> --> 515 raise TypeError, "cannot coerce type '%s' into a
> SymbolicExpression."%type(x)
> 516
> 517 def _repr_(self):
>
> TypeError: cannot coerce type '<type 'tuple'>' into a SymbolicExpression.
> sage: f=(x+y,x-2*y)
> sage: f(x=2,y=3)
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call last)
>
> /home/grout/.sage/temp/good/18016/_home_grout__sage_init_sage_0.py in
> <module>()
>
> TypeError: 'tuple' object is not callable
> sage: f=vector((x+y,x-2*y))
> sage: f(x=2,y=3)
> (5, -4)
>
>
> Jason
>
>
> >
>
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