       Re: problems with delayed write: tag list

• To: mathgroup at smc.vnet.net
• Subject: [mg79908] Re: problems with delayed write: tag list
• From: Bill Rowe <readnewsciv at sbcglobal.net>
• Date: Wed, 8 Aug 2007 04:57:48 -0400 (EDT)

```On 8/7/07 at 1:38 AM, peter_van_summeren at yahoo.co.uk (P_ter) wrote:

>I have a list of elements of two numbers:

>myList ={{1,2},{2,7},..}.

>The first number is in this case always the
>position. I want to know when the difference is a certain
>value,myDiff, eg. 5

>i=1;myDiff==5;
>now= Reap[While[i<Length[myList],i++;
>If[myList[[i,2]]-myList[[i,1]]==myDiff,Sow[i]]];w]

>My question is: how do I make "nowFunction[myDiff_]:="? I run into
>tag list errors in the definition when I try that. P_ter

It seems to me your code is more complex than necessary. Using
either Cases seems to me to be more efficient. First, generate
some data:

In:= data =
MapIndexed[Join[#2, {#1}] &, RandomInteger[{1, 20}, 20]]

Out= {{1, 9}, {2, 18}, {3, 8}, {4, 4}, {5, 15}, {6, 19},
{7, 8}, {8, 4}, {9, 18}, {10, 3}, {11, 19}, {12, 8},
{13, 20}, {14, 17}, {15, 12}, {16, 11}, {17, 1},
{18, 14}, {19, 13}, {20, 12}}

In:= diff = 5;

In:= Cases[data, _?(Subtract @@ # == -diff &)][[All, 1]]

Out= {3}

Then nowFunction would be:

nowFunction[diff_, data_] :=
Cases[data, _?(Subtract @@ # == -diff &)][[All, 1]]
--
To reply via email subtract one hundred and four

```

• Prev by Date: Re: Projectile motion
• Next by Date: Re: How to extract generated plot data (or mesh data) from a Graphics3D
• Previous by thread: Re: problems with delayed write: tag list
• Next by thread: Re: problems with delayed write: tag list