[R] filling small gaps of N/A

[jim holtman]

> x <- read.table(text="09/01/2008 12:00      1.93
+ 09/01/2008 12:15      3.93
+ 09/01/2008 12:30       NA
+ 09/01/2008 12:45       NA
+ 09/01/2008 13:00      4.93
+ 09/01/2008 13:15      5.93
+ 09/01/2008 16:15                2.93
+ 09/01/2008 16:30                2.93
+ 09/01/2008 16:45                NA
+ 09/01/2008 17:00                NA
+ 09/01/2008 17:15                NA
+ 09/01/2008 17:30                NA
+ 09/01/2008 17:45                NA
+ 09/01/2008 18:00                NA
+ 09/01/2008 18:15                NA
+ 09/01/2008 18:30                NA
+ 09/01/2008 18:45                NA
+ 09/01/2008 19:00                NA
+ 09/01/2008 19:15                NA
+ 09/01/2008 19:30                NA
+ 09/01/2008 19:45                NA
+ 09/01/2008 20:00                NA
+ 09/01/2008 20:15                7.93
+ 09/01/2008 20:30                7.93", as.is = TRUE)
>
> # find the NA gaps and process differently
> gaps <- rle(is.na(x$V3))
> offsets <- c(1, cumsum(head(gaps$lengths, -1)) + 1)
> (shortgaps <- which(gaps$values & (gaps$lengths <= 4)))
[1] 2
> (longgaps <- which(gaps$values & (gaps$lengths > 4)))
[1] 4
>
> # now that you have the indices of where the short/long gaps are
> # you can process each individually; left as an exercise to the reader
>


On Tue, Apr 3, 2012 at 10:13 AM, jeff6868
<geoffrey_klein at etu.u-bourgogne.fr> wrote:
> Michael,
>
> First of all, thank you very much for your answer.
> I've read your 2 answers, but I'm not really sure that they corresponds to
> my problem of NAs.
> I'll try to detail you a bit more.
>
> This problem concerns the second part of my program. In the first part, I've
> already created a timeseries object with the library (timeseries). I had to
> delete first all the wrong values in my data and replace it with NAs.
> So my data contains already missing data (NAs), as I have cleaned it before.
>
> The thing is that sometimes I have small gaps of missing data (only 2 or 3
> following) like in "example 1" below:
>
> example 1:
>
> 09/01/2008 12:00      1.93
> 09/01/2008 12:15      3.93
> 09/01/2008 12:30       NA            So here you have a small gap with only
> 2 NAs
> 09/01/2008 12:45       NA
> 09/01/2008 13:00      4.93
> 09/01/2008 13:15      5.93
>
> But sometimes, always in the same file, I have big gaps, such as 10 or more
> NAs following each other like in "example 2" below:
>
> example 2:
>
> 09/01/2008 16:15                2.93
> 09/01/2008 16:30                2.93
> 09/01/2008 16:45                NA
> 09/01/2008 17:00                NA
> 09/01/2008 17:15                NA
> 09/01/2008 17:30                NA
> 09/01/2008 17:45                NA
> 09/01/2008 18:00                NA          So here you have a big gap with more than 10
> NAs following each other
> 09/01/2008 18:15                NA
> 09/01/2008 18:30                NA
> 09/01/2008 18:45                NA
> 09/01/2008 19:00                NA
> 09/01/2008 19:15                NA
> 09/01/2008 19:30                NA
> 09/01/2008 19:45                NA
> 09/01/2008 20:00                NA
> 09/01/2008 20:15                7.93
> 09/01/2008 20:30                7.93
>
> So in the whole same file, I can have sometimes big gaps (2 or 3 NAs),
> sometimes big or very big gaps (10 or 100 NAs following).
>
> The aim of my problem is to apply the function: na.approx(x) of the library
> (zoo) to fill NAs ONLY for small gaps.
>
> If I just do: apply(na.approx(x)), it will fill all the NAs of my data (big
> gaps + small gaps). It's exactly what I DON'T WANT.
>
> My problem is to say to R: " you apply the function (na.approx) to fill NAs
> ONLY if you see 4 NAs maximum following each other (small gaps) (like
> example 1)". "If you see more than 4 NAs following each other (big gaps like
> in example 2), you keep these NAs and you DON'T fill this big gap".
>
> My question is: how can I say this to R? I don't know how to do it.
> Hope I've been understandable this time ^^
> Thanks a lot again for all your answers!
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/filling-small-gaps-of-N-A-tp4528184p4528907.html
> Sent from the R help mailing list archive at Nabble.com.
>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.