Re: [R] sequentially process a list

From: Mike Lawrence <Mike.Lawrence_at_dal.ca>
Date: Mon, 21 May 2007 12:56:17 -0300

Try nested ifelse() statements to label the group

ex.
time$group=ifelse(time$time<5,NA,

	ifelse(time$time<9,1,
		ifelse(time$time<13,NA,
			ifelse(time$time<17,2,NA)
		)
	)

)

Then use aggregate to find the max value.

ex.
time.max=aggregate(time$value,list(group=time$group),max)

On 21-May-07, at 6:39 AM, Robert wrote:

> Hi dear R users,
>
> I'm a R beginner and I have a basic question about sequential
> treatments of lists.
>
> I have a time based (i.e. events are consecutive) list of values of
> a biological property.
>
> Like :
>
> time value
> 1 5
> 2 10
> 3 7
> 4 10
> 5 19
> 6 21
> 7 20
> 8 18
> 9 10
> 10 7
> 11 8
> 12 12
> 13 17
> 14 19
> 15 24
> 16 18
> 17 15
> 18 10
> 19 9
> [...]
>
>
> And I have to define a threshold and to attach each event to his
> group, i.e. values upper the threshold.
>
> Like, for a threshold value of 17
>
> time value group
> 1 5 NA
> 2 10 NA
> 3 7 NA
> 4 10 NA
> 5 19 1
> 6 21 1
> 7 20 1
> 8 18 1
> 9 10 NA
> 10 7 NA
> 11 8 NA
> 12 12 NA
> 13 17 2
> 14 19 2
> 15 24 2
> 16 18 2
> 17 15 NA
> 18 10 NA
> 19 9 NA
> [...]
>
>
> The only solution that I have found is to do a sequentially read
> and write :
> for(i in 1:length(my_events_list))
> {
> [...]
> }
>
> But I very slow. Do you have another ideas ?
>
> And after I need to extract maximum values for each group
> Like :
> group max_value
> 1 21
> 2 24
> [...]
>
> and for each event which is part of a group to know if is't a
> ascending phase or no.
>
>
> Yes, lot of questions !! Sorry, but I think that the solution may
> be unique.
>
> In advance, thank you a lot
>
> regards
>
> JS
>
>
>
>
>
>
>
>
> ______________________________________________________________________
> _______
>
> ______________________________________________
> R-help_at_stat.math.ethz.ch mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

--
Mike Lawrence
Graduate Student, Dalhousie University Department of Psychology
http://myweb.dal.ca/mc973993

"The road to wisdom? Well, it's plain and simple to express:
Err and err and err again, but less and less and less."
- Piet Hein

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Received on Mon 21 May 2007 - 16:39:18 GMT

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