> Does anyone have any thoughts on how to code this, perhaps using the NA
> values as a "break point"?
You can count the cumulative number of NA breakpoints in a vector
with cumsum(is.na(vector)), as in
> cbind(d, LeakNo=with(d, cumsum(is.na(lon)|is.na(lat)|is.na(CH4))))
lon lat CH4 LeakNo
1 -71.11954 42.35068 2.595834 0
2 -71.11954 42.35068 2.595688 0
3 NA NA NA 1
4 NA NA NA 2
5 NA NA NA 3
6 -71.11948 42.35068 2.435762 3
7 -71.11948 42.35068 2.491003 3
8 NA NA NA 4
9 -71.11930 42.35068 2.464475 4
10 -71.11932 42.35068 2.470865 4
Add 1 if you want to start with 1. If you only want to increase the count
after each sequence of NA's then you could use rle() or
> na <- with(d, is.na(lon)|is.na(lat)|is.na(CH4))
> cbind(d, LeakNo=cumsum(c(TRUE, na[-1] < na[-length(na)])))
lon lat CH4 LeakNo
1 -71.11954 42.35068 2.595834 1
2 -71.11954 42.35068 2.595688 1
3 NA NA NA 1
4 NA NA NA 1
5 NA NA NA 1
6 -71.11948 42.35068 2.435762 2
7 -71.11948 42.35068 2.491003 2
8 NA NA NA 2
9 -71.11930 42.35068 2.464475 3
10 -71.11932 42.35068 2.470865 3
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of Max Brondfield
> Sent: Wednesday, May 23, 2012 1:42 PM
> To: r-help@r-project.org
> Subject: [R] Using NA as a break point for indicator variable?
>
> Hi all,
> I am working with a spatial data set for which I am only interested in high
> concentration values ("leaks"). The low values (< 90th percentile) have
> already been turned into NA's, leaving me with a matrix like this:
>
> < CH4_leak
>
> lon lat CH4
> 1 -71.11954 42.35068 2.595834
> 2 -71.11954 42.35068 2.595688
> 3 NA NA NA
> 4 NA NA NA
> 5 NA NA NA
> 6 -71.11948 42.35068 2.435762
> 7 -71.11948 42.35068 2.491003
> 8 NA NA NA
> 9 -71.11930 42.35068 2.464475
> 10 -71.11932 42.35068 2.470865
>
> Every time an NA comes up, it means the "leak" is gone, and the next valid
> value would represent a different leak (at a different location). My goal
> is to tag all of the remaining values with an indicator variable to
> spatially distinguish the leaks. I am envisioning a simple numeric
> indicator such as:
>
> lon lat CH4 leak_num
> 1 -71.11954 42.35068 2.595834 1
> 2 -71.11954 42.35068 2.595688 1
> 3 NA NA NA NA
> 4 NA NA NA NA
> 5 NA NA NA NA
> 6 -71.11948 42.35068 2.435762 2
> 7 -71.11948 42.35068 2.491003 2
> 8 NA NA NA NA
> 9 -71.11930 42.35068 2.064475 3
> 10 -71.11932 42.35068 2.070865 3
>
> Does anyone have any thoughts on how to code this, perhaps using the NA
> values as a "break point"? The data set is far too large to do this
> manually, and I must admit I'm completely at a loss. Any help would be much
> appreciated! Best,
>
> Max
>
> [[alternative HTML version deleted]]
>
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