Re: modified list interval calculation

• To: mathgroup at smc.vnet.net
• Subject: [mg21221] Re: modified list interval calculation
• From: Pasquale Nardone <Pasquale.Nardone at ulb.ac.be>
• Date: Mon, 20 Dec 1999 02:27:43 -0500 (EST)
• Organization: Brussels Free Universities VUB/ULB
• References: <831tsm\$fmj@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```
Deborah Leddon wrote:

> Hi,
> I am having trouble with the problem below:
>
> I am trying to remove from list, t, those numbers in list, nt, that
> match and then I want to calculate the differences (intervals )
> between succesive numbers in list, t, that do not contain the
> removed number. For example:
> the two lists are;
> t = {1,4,4.5,6,7,8,8.9,9,10,12,140,16,16.8,17,18,
>         19,19.1,19.3,19.5,20}
> nt = {8,8.9,10,17}
>
> the resulting intervals would look like:
> 4 -1, 4.5 - 4, 6 - 4.5, 7 - 6, 140 -12, 16 - 140, 16.8 - 16, 19 - 18,
> 19.1 -19, 19.3 - 19.1, 19.5 - 19.3, 20 - 19.5
> and of course the final list would be:
> intervals = {3, .5, 1.5, 1, 128, -124, .8, 1, .1, .2, .2, .5};
>
> Note that 9 was omitted from the calculation of intervals because it
> would have been involved in a calculation with a removed number
> from the list, t.
>
> Thanks in advance if anyone can help.
>
> Regards, Debbie

try this one:

First build a pairs of elements
res = Drop[Transpose[{t, RotateLeft[t]}], -1]
{{1, 4}, {4, 4.5}, {4.5, 6}, {6, 7}, {7, 8}, {8, 8.9}, {8.9, 9}, {9,
10}, {10,12},
{12, 140}, {140, 16}, {16, 16.8}, {16.8, 17}, {17, 18}, {18, 19},
{19, 19.1}, {19.1, 19.3}, {19.3, 19.5}, {19.5, 20}}

Then rebuild a new list with elements extracted
ListOut = {};
Do[
If[Intersection[res[[i]], nt] == {}, AppendTo[ListOut, res[[i]]]],
{i, 1, Length[res]}]

ListOut contains the corrected serie

In[47]:=
ListOut

Out[47]=
{{1, 4}, {4, 4.5}, {4.5, 6}, {6, 7}, {12, 140}, {140, 16}, {16, 16.8},
{18,
19}, {19, 19.1}, {19.1, 19.3}, {19.3, 19.5}, {19.5, 20}}

Then apply the  difference to that list:

In[54]:=
-Apply[Subtract, ListOut, 1]

Out[54]=
{3, 0.5, 1.5, 1, 128, -124, 0.8, 1, 0.1, 0.2, 0.2, 0.5}

OR

In[55]:=
Map[#.{-1, 1} &, ListOut]

Out[55]=
{3, 0.5, 1.5, 1, 128, -124, 0.8, 1, 0.1, 0.2, 0.2, 0.5}

OR

In[59]:=
Map[(#[[2]] - #[[1]]) &, ListOut]

Out[59]=
{3, 0.5, 1.5, 1, 128, -124, 0.8, 1, 0.1, 0.2, 0.2, 0.5}

--------------------------------------------
Pasquale Nardone                          *
Universite Libre de Bruxelles             *
CP 231, Sciences-Physique-Agrigation      *
Bld du Triomphe                           *
1050 Bruxelles, Belgium                   *
tel: 650,55,15 fax: 650,57,67 (+32,2)     *
http://homepages.ulb.ac.be/~pnardon/       *
--------------------------------------------

```

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