Re: Product over an arbitrary index.

*To*: mathgroup at smc.vnet.net*Subject*: [mg68692] Re: [mg68683] Product over an arbitrary index.*From*: Sseziwa Mukasa <mukasa at jeol.com>*Date*: Thu, 17 Aug 2006 04:17:51 -0400 (EDT)*References*: <200608160736.DAA06150@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

On Aug 16, 2006, at 3:36 AM, quantieny at gmail.com wrote: > I have a function f(x,y) that I would like to compute the product > over indices i,j > where i goes from an arbitrary list {1,4,3} and j goes 1 to m. This statement is a little unclear, are you taking the product f[i,j] where i is the sequence {1,4,3}, j is 1..m? The way to do this in Mathematica is to store the sequence for i in a list and use the index of the iterator in product to get the appropriate sequence element. If your sequence is very long but you have a generating function, just pass the index to the generating function. > Is this possible in mathematica the function Product itself seems to > only work over a continous sequence and it is not clear how I can use > two set of indices. You can specify as many indices as you want for example iSequence={1,4,3}; m=50; Product[f[iSequence[[i]],j],{i,Length[iSequence]},{j,m}] > Additionally can I specify the product over an intersection or > complement of a list?. Using the technique above you can do pretty much anything you want, all you need is a function that maps an index to a sequence value. Regards, Ssezi

**References**:**Product over an arbitrary index.***From:*quantieny@gmail.com