Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.soft-sys.math.mathematica > #2763 > unrolled thread
| Started by | ferradini <gianmarco.ferradini@email.it> |
|---|---|
| First post | 2011-05-28 11:20 +0000 |
| Last post | 2011-05-29 11:36 +0000 |
| Articles | 2 — 2 participants |
Back to article view | Back to comp.soft-sys.math.mathematica
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
| From | ferradini <gianmarco.ferradini@email.it> |
|---|---|
| Date | 2011-05-28 11:20 +0000 |
| Subject | how to calculate an index and vice versa |
| Message-ID | <irqlpg$e9a$1@smc.vnet.net> |
given n numbers (eg. 1 to 90) I can build the following list of numbers k (in this case 4) 1, 2, 3, 4 associated index -> 0 1, 2, 3, 5 associated index -> 1 1, 2, 3, 6 associated index -> 2 1, 2, 3, 7 associated index -> 3 1, 2, 3, 8 ................... .... 1, 2, 3, 9 ....................... ....................... ....................... 10, 41, 60, 61 associated index -> 954722 ....................... ....................... 87, 88, 89, 90 associated index -> 2555190 I need to build an algorithm to assign eg 4 elemnti can obtain its index in the list (1, 2, 3, 7 return 3) The second algorithm is 'inverse: given a number such as 954722 I get the four elements 87; 88, 89, 90. The elemnti in the list are always sorted values. I thank those who will send me information on the subject to follow Thank ferradini
[toc] | [next] | [standalone]
| From | Ray Koopman <koopman@sfu.ca> |
|---|---|
| Date | 2011-05-29 11:36 +0000 |
| Message-ID | <irtb3n$pim$1@smc.vnet.net> |
| In reply to | #2763 |
On May 28, 4:20 am, ferradini <gianmarco.ferrad...@email.it> wrote: > 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 You want RankKSubset and UnrankKSubset, in Combinatorica.
[toc] | [prev] | [standalone]
Back to top | Article view | comp.soft-sys.math.mathematica
csiph-web