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Re: Operating on every k-th element of list?

• To: mathgroup at smc.vnet.net
• Subject: [mg37124] Re: [mg37080] Operating on every k-th element of list?
• From: Bill Rowe <listuser at earthlink.net>
• Date: Thu, 10 Oct 2002 03:21:18 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

On 10/8/02 at 7:17 AM, siegman at stanford.edu (AES) wrote:

>I want to apply a function to every  k-th  element of a long list and
>add the result to the  k+1  element.
>
>[Actually  k = 3  and I just want to multiply  myList[[k]]  by a
>constant (independent of k)  and add the result to  myList[[k+1]]  for
>every value of  k  that's divisible by 3.]

If I understand what you are trying to do correctly, the following should work

(f[#[[1]]+#[[2]])&/@Partition[Drop[list,k-1],2,k]

Here f is the function you want applied to the k-th element