[R] Re membering the last time an event occurred within a dataframe

[Jim Price]

Many thanks; using Gabor's advice I'd used:

with(myData, rep(time, evid)[cumsum(evid)])

but yours also works a treat Henrique.

Thanks once again!

Jim.



Henrique Dallazuanna wrote:
> 
> If I understand, try this:
> 
> with(myData, factor(cumsum(evid), labels = which(evid == 1)))
> 
> 
> On Thu, Jul 3, 2008 at 3:19 PM, Jim Price <price_ja at hotmail.com> wrote:
> 
>>
>> All,
>>
>> I am constructing a pharmacokinetic dataset and have hit a snag. The
>> dataset
>> can be demonstrated in the following way:
>>
>>
>>
>> myData <- data.frame(
>>        evid = c(1, 0, 0, 0, 1, 0, 1, 1, 1, 0),
>>        time = 1:10,
>>        last.dose.time = c(1, 1, 1, 1, 5, 5, 7, 8, 9, 9)
>> )
>>
>>
>> The evid field is an indicator variable for whether the associated
>> observation is a dosing record (when it takes value 1) or an observation
>> (where it takes value 0). The time field is a date-time record for the
>> associated dose / observation event. I'm trying to calculate the time
>> since
>> the last dose for each observation event - to support that, the data I'd
>> like to end up with is contained in last.dose.time, which gives the time
>> at
>> which the last dosing event occured.
>>
>> The problem is in calculating the last.dose.time field; this is the first
>> time I've done this particular kind of data manipulation in R and I just
>> can't get my head around the code to solve it.
>>
>> I've been eyeballing rle and I think there may be a solution hiding in
>> there
>> somewhere, but I'm still failing to progress. Any help would be
>> appreciated!
>>
>>
>> Thanks in advance,
>>
>> Jim Price
>> Cardiome Pharma. Corp.
>>
>> --
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>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
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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.
>>
> 
> 
> 
> -- 
> Henrique Dallazuanna
> Curitiba-Paraná-Brasil
> 25° 25' 40" S 49° 16' 22" O
> 
> 	[[alternative HTML version deleted]]
> 
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> 

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