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Re: How to express a Product (special case) in Mathematica?


In case of non singular expression that you need to skip, dont skip it
and then divide by this term.
In case it is singular  (as I have seen in the given site) you
generate a list with 1 replacing the skipped expression and then Apply
Times on the list
the following is just a simple (but yet demonstrative enough) for both cases
skipProd1[j_Integer] := Product[f[i], {i, 10}]/f[j](* non singular case *)
skipProd2[j_Integer] := Times @@ Table[If[i == j, 1, f[i]], {i, 10}](*
singular case*)
regards
yehuda

On 7/28/05, vdavidster at gmail.com <vdavidster at gmail.com> wrote:
> If you're familiar with the Lagrange interpolation polynomial, you'll
> know that the coefficient term, phi, is defined as follows:
> 
>             n
> phi_j (t) = TT     (t - t_i)
>             i=0   -----------
>             i!=j  (t_j - t_i)
> 
> Or in LaTeX notation:
> 
> \phi_j(t) = \prod^{n}_{\stackrel{i=0}{i \neq j}} \frac{(t - t_i)}{(t_j
> - t_i)}
> 
> Or in graphical form:
> http://mathworld.wolfram.com/LagrangeInterpolatingPolynomial.html
> 
> How do I do that in Mathematica?
> How do I specify a product that skips a value in its iterator, i? (i.e.
> i != j)
> 
> Thanks!
> 
> David
> 
>


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