Re: Style Question: The Functional Way

*To*: mathgroup at smc.vnet.net*Subject*: [mg115806] Re: Style Question: The Functional Way*From*: Just A Stranger <forpeopleidontknow at gmail.com>*Date*: Fri, 21 Jan 2011 04:32:03 -0500 (EST)

Of course that function would exist. Thank you for pointing that out. :) On Thu, Jan 20, 2011 at 4:39 AM, Bob Hanlon <hanlonr at cox.net> wrote: > DeltaList[L_] := Subtract @@@ Reverse /@ Partition[L, 2, 1] > > data = Array[x, 10]; > > The simplest way is to just use Differences or ListCorrelate. > > DeltaList[data] == > Differences[data] == > ListCorrelate[{-1, 1}, data] == > Most[RotateLeft[data] - data] == > ({-1, 1}.# & /@ Partition[data, 2, 1]) > > True > > > Bob Hanlon > > ---- Just A Stranger <forpeopleidontknow at gmail.com> wrote: > > ============= > Hello, > > So I'm trying to learn how to do things the functional way. As an exercise > I'm trying to program a simple economics related table that gives revenue, > marginal revenue, etc given a demand schedule (2 lists of numbers > representing quantity and price respectively). A simple task in a > spreadsheet. > > The point is that I need a list of the differences in the given lists, from > which I will be using to get marginal values (derivatives). I'll call it, > say, DeltaList, and I was wondering if this would be a proper "functional" > way to go about the task: > > > > > In[0]: DeltaList[L_] := Subtract @@@ Reverse /@ Partition[L, 2, 1] > > (DelatList: list -> list) > > > Basically, it partitions the list into ordered pairs, reverses those > ordered > pairs to prep them for the subsequent Subtract application. > > Is this the right way to think about this (painfully simple) problem in a > functional way? > > Thank you. All of you have been most helpful in the past. > > >