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Map and functional constructs to replace iterative statements

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96783] Map and functional constructs to replace iterative statements
  • From: Andreas <aagas at ix.netcom.com>
  • Date: Wed, 25 Feb 2009 04:00:50 -0500 (EST)

I have begun to replace Table, Do, While, or For, but in my thinking with Map, Inner, Outer and other functional programming constructs as I learn more about Mathematica.

But, I'm stuck.  I need to figure out how to use Map (or some related approach) when a function needs both a current value and a previous value in a time series, such as a percentage change function (or perhaps more generally stated, when I need to refer to previous values in a series or even previous calculations).  But first a simple case:

percentChange[currentValue_, previousValue_] := 100 * ( currentValue - previousValue) / previousValue

I know how to apply this iteratively, but how can I do it with Map or some other functional construct?

Say I have a list: timeSeries 

I thought to try something like this:

Map[percentChange[?,?], timeSeries] 

but I don't know how what to put in for "?".

Any help much appreciated.

Thx.


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