[R] Using NA as a break point for indicator variable?

[Rui Barradas]

Hello,

Assuming that 'd' is your original data.frame and that you've set entire 
rows to NA, try this


d$leak_num <- NA
ix <- !is.na(d[, 1])  # any column will do, entire row is NA
## alternative, if other rows may have NAs, due to something else
#ix <- apply(d, 1, function(x) all(!is.na(x)))
r <- rle(ix)
v <- cumsum(r$values)
d$leak_num[ix] <- rep(v[r$values], r$lengths[r$values])
d


Hope this helps,

Rui Barradas

Em 24-05-2012 11:00, Max Brondfield <mbrondf at post.harvard.edu> escreveu:
> Date: Wed, 23 May 2012 16:42:02 -0400
> From: Max Brondfield<mbrondf at post.harvard.edu>
> To:r-help at r-project.org
> Subject: [R] Using NA as a break point for indicator variable?
> Message-ID:
> 	<CADu+jDpcJUHZTXxrsxyQvjaEmw_N0iLbL6ZJjHZC-rSBCMneiw at mail.gmail.com>
> Content-Type: text/plain
>
> 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
>
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>
>