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Re: Map and functional constructs to replace iterative statements

On Feb 25, 2009, at 4:00 AM, Andreas wrote:

> 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?

One option is to use create the pairs of arguments, then apply the  


Another option is to do it recursively:




I realize the recursive solution does not use functional programming  
constructs but I've found that not having to worry about explicit  
indices can result in less bugs.


Sseziwa Mukasa

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