R help - Nov 2001 - More of a stats question I suppose...

Hi all.  Sorry to post this here, but I figure that you may know the answer to
my question...

I analyze data sets very frequently, and it becomes cumbersome to try to find
sustained peaks (my def - high points that exist for
about 6 minutes or more - 3 poll intervals) in these data sets all the time. 
Right now I graph the data and then look for what
looks to be a sustained peak and then go to the raw data itself to make the
determination.  I'm actually embarassed to say that I do
that because it is SO time consuming and I'm sure there are other ways.  I
just haven't had the time to explore them.  Well, now
it's becoming more critical.

So, here's my question - can anyone suggest a good method using R to analyze
a set of data that consists of time (polled every 2
minutes) and values at that time, so that I can just plop the data set in, and
then have R find sustained peaks?  Maybe then it can
report them to me, or just point out the poll intervals where they occurred... 
Or something like that...

Any ideas?  Does my question make sense? =)

Thanks in advance.  I'd really appreciate any help I can get on this.

Chris

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On Thu, 1 Nov 2001, Chris Milkosky wrote:
> Hi all.  Sorry to post this here, but I figure that you may know the answer
to my question...
>
> I analyze data sets very frequently, and it becomes cumbersome to try to
find sustained peaks (my def - high points that exist for
> about 6 minutes or more - 3 poll intervals) in these data sets all the
time.  Right now I graph the data and then look for what
> looks to be a sustained peak and then go to the raw data itself to make the
determination.  I'm actually embarassed to say that I do
> that because it is SO time consuming and I'm sure there are other ways.
I just haven't had the time to explore them.  Well, now
> it's becoming more critical.
>
> So, here's my question - can anyone suggest a good method using R to
analyze a set of data that consists of time (polled every 2
> minutes) and values at that time, so that I can just plop the data set in,
and then have R find sustained peaks?  Maybe then it can
> report them to me, or just point out the poll intervals where they
occurred...  Or something like that...
>
Suppose x is your series and you want to find more than LONG consecutive
values equal to HIGH or greater

p<-cumsum(x>HIGH)
padding<-rep(0,LONG)
longpeaks<-which(c(padding,p)+LONG==c(p,padding))

longpeaks now contains the index of the start of each long peak (in fact
it contains all but the first LONG-1 indices of each long peak, but that
shouldn't matter).

	-thomas


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