Re: Re: finding the position of a pattern in list
- To: mathgroup at smc.vnet.net
- Subject: [mg64617] Re: Re: [mg64583] finding the position of a pattern in list
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Fri, 24 Feb 2006 00:18:12 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
Here is a faster method than the one that I first suggested.
pos1[data_]:=Position[Partition[data,2,1],{0,1}]//Flatten;
pos2[data_]:=Position[RotateLeft[data]-data,1]//Flatten;
data=Table[Random[Integer],{100000}];
pos1[data]==pos2[data]
True
Timing[pos1[data]][[1]]
0.39032 Second
Timing[pos2[data]][[1]]
0.128189 Second
Bob Hanlon
>
> From: Bob Hanlon <hanlonr at cox.net>
To: mathgroup at smc.vnet.net
> Subject: [mg64617] Re: [mg64583] finding the position of a pattern in list
>
> data={0,0,1,1,1,0,0,1,1,1,0};
>
> Position[Partition[data,2,1],{0,1}]//Flatten
>
> {2,7}
>
>
> Bob Hanlon
>
> >
> > From: Gang Ma <contactmagang at gmail.com>
To: mathgroup at smc.vnet.net
> > Subject: [mg64617] [mg64583] finding the position of a pattern in list
> >
> > Hi,
> > I am working on a program to do the following: My data is a list of 0
> > and 1. For example, {0,0,1,1,1,0,0,1,1,1,0}. I want to find the
> > positions of all the pattern of {0,1}. In my previous example, the
> > first {0,1} is at 2 and and the second {0,1} appears at 7. I can
> > write a loop to do this, but I have several thousands such lists,
> > the computation will be time consuming using loop.
> >
> > My question is whether it is possible to use the pattern match to do
> > this quickly. If not for the list, do I need to convert the list to
> > string then use some pattern match for string? Thank you very much.
> >
> > regards,
> >
> > Gang Ma
> >
> >
> >
> >
>