On Mon, Jan 9, 2012 at 7:42 AM, Matthew <[email protected]> wrote:
> You could do the above by explicitly making a scalar symbol for each
> of x[0], x[1], ...
>
>>>> x,y,z = symbols('x y z')
>>>> X = Matrix([[x], [y], [z]])
>>>> f = 5*X[0]**2 + 5*X[1]**2 + 5*X[2]**2
>
>>>> Matrix([f]).jacobian(X)
> [10⋅x 10⋅y 10⋅z]
>
>>>> Matrix([f]).jacobian(X) * ones(3,1) # inner product with ones vector to sum
> [10⋅x + 10⋅y + 10⋅z]
>
> I believe there is a clean way to make a bunch of symbols x0, x1, x2,
> x3, ... easily using the symbols function. I just don't know it.
symbols('x0:10') will produce x0, x1, ..., x9. If you want an
indeterminate amount of symbols, use numbered_symbols().
Aaron Meurer
>
>
> On Jan 8, 6:41 pm, Alan Bromborsky <[email protected]> wrote:
>> On 01/08/2012 07:06 PM, John B wrote:
>>
>>
>>
>>
>>
>>
>>
>> >> You might find section 11.1 in "Geometric Algebra for Physicists" by
>> >> Doran and Lasenby relevant. Also go
>> >> tohttp://www.montgomerycollege.edu/Departments/planet/planet/Numerical_...
>> >> and download bookGA.pdf. and look at chapter 6.
>> > Hello Alan:
>> > Thanks, but perhaps my example did not help to explain my real
>> > question. Here is a more simple statement of my question. Is there a
>> > way to use sympy to differentiate, for example, the function:
>>
>> > f = 5*x[0]**2 + 5*x[1]**2 + ...5*x[n]**2, where x is in vector or
>> > matrix form to obtain the symbolic answer df/dx =
>>
>> > Sum(10*x[i], (i,0,n))
>>
>> > That is, is there some way to write in sympy (Sum(5*x[i]**2, (i,
>> > 0,n))).diff()?
>> > John
>>
>> Is x[j] a vector or matrix or is x = (x[0],...,x[n]) the vector for the
>> vector case, then how would you write the matrix case?
>
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