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MathGroup Archive 2006

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RE: a simple product, but with "i = 1...n AND i != x"

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70262] RE: [mg70243] a simple product, but with "i = 1...n AND i != x"
  • From: "David Park" <djmp at earthlink.net>
  • Date: Tue, 10 Oct 2006 06:12:19 -0400 (EDT)

You would have to specify n as a parameter, and in order to do the test x
would have to be at least numeric.

f[n_Integer?Positive][x_?NumericQ] :=
  Module[{i, work},
    work = Table[x - i, {i, 1, n}];
    work = Select[work, N[#] != 0 &];
    Times @@ work]

f[7][6]
-120

f[7][6.2]
-29.5207

Maybe you meant x to always be an integer?

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

From: xarnaudx at gmail.com [mailto:xarnaudx at gmail.com]
To: mathgroup at smc.vnet.net


hi,
i would like to make a function like
f[x_] := Product[x - i, {i, 1, n} AND i != x}

obviously, the end of the expression is syntactically incorrect. But
how to rewrite this product correctly?
thanks



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