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Groups > comp.soft-sys.math.mathematica > #2763

how to calculate an index and vice versa

From ferradini <gianmarco.ferradini@email.it>
Newsgroups comp.soft-sys.math.mathematica
Subject how to calculate an index and vice versa
Date 2011-05-28 11:20 +0000
Organization Steven M. Christensen and Associates, Inc and MathTensor, Inc.
Message-ID <irqlpg$e9a$1@smc.vnet.net> (permalink)

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given n numbers (eg. 1 to 90)
I can build the following list of numbers k (in this case 4)

1, 2, 3, 4 associated index -> 0
1, 2, 3, 5 associated index -> 1
1, 2, 3, 6 associated index -> 2
1, 2, 3, 7 associated index -> 3
1, 2, 3, 8 ................... ....
1, 2, 3, 9 .......................
.......................
.......................
10, 41, 60, 61 associated index -> 954722
.......................
.......................
87, 88, 89, 90 associated index -> 2555190
I need to build an algorithm to assign eg 4 elemnti can obtain its index 
in the list
(1, 2, 3, 7 return 3)

The second algorithm is 'inverse: given a number such as 954722 I get 
the four elements 87; 88, 89, 90.
The elemnti in the list are always sorted values.

I thank those who will send me information on the subject to follow
Thank ferradini

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how to calculate an index and vice versa ferradini <gianmarco.ferradini@email.it> - 2011-05-28 11:20 +0000
  Re: how to calculate an index and vice versa Ray Koopman <koopman@sfu.ca> - 2011-05-29 11:36 +0000

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