[R] filling small gaps of N/A

[jeff6868]

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!



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