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MathGroup Archive 1993

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Re: Lists

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Re: Lists
  • From: Boss Man <BOSS at noaapmel.gov>
  • Date: Tue, 16 Mar 1993 14:14 PDT

Richard writes:
-----------------------------------
I am having a difficult time dealing with lists.
I have a list of data :

{{1,2},{2,3},{4,5}}

I want to do some operations on the second column only.
Such as +1, Sin[], etc to each element in the second
column.  I admit I only have a rudimentary knowledge
of Map, Apply, Transpose, and Flatten.  Any help would 
be appreciated.

Also, I have data that needs several fitting equations.
One will be Exp[a x -b], another Exp[-c x+d], and the
last would be a polynomial.  Then I would like to Plot
the data and fitting equations in there respective 
regions at the same time.  I have seen something
like this before, but I can't remember where.

Thanks

Richard
----------------------------------------

Try using map and Transpose as in the following examples:

a = {{1,2},{2,3},{4,5}}
{{1, 2}, {2, 3}, {4, 5}}
b = Map[(# + 1)&, Transpose[a][[2]]]
{3, 4, 6}
c = Map[(Sin[#])&, Transpose[a][[2]]]
{Sin[2], Sin[3], Sin[5]}

It seems there must be a more elegant way to do this, but this
may get you started.

Ed Boss
NOAA/PMEL




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