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MathGroup Archive 2001

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Re: Complicated Rotation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg27262] Re: Complicated Rotation
  • From: Tom Burton <tburton at cts.com>
  • Date: Wed, 14 Feb 2001 03:41:29 -0500 (EST)
  • Organization: Brahea Consulting
  • References: <96as1b$6ep@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hello Yas,

What seems to be required to is successively premultiply r[t] for t=t1,t2,t3,... to s0. I like to this kind of thing as follows. I'll assume that the increment in t takes on whole numbers. Define the matrix r[t] along the lines of your memo. Then

In[50]:=
FoldList[r[#2] . #1 & , s0,  Range[5]]

Out[50]=
{s0, 
 r[1] . s0, 
 r[2] . r[1] . s0, 
 r[3] . r[2] . r[1] . s0, 
 r[4] . r[3] . r[2] . r[1] . s0,
 r[5] . r[4] . r[3] . r[2] . r[1] . s0}

This is very simple and easy to read, once you understand FoldList. 

Tom

On 13 Feb 2001 03:42:19 -0500, in comp.soft-sys.math.mathematica you wrote:

>Dear mathgroup,
>I have a problem that I have been trying to do in mathematica...
>And at successive increments of time
>
>sf[1] = r[1]*s0
>sf[2] = r[2]*sf[1]
>sf[3] = r[3]*sf[2]
>|
>|
>sf[n] = r[n]*sf[n-1]

Tom


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