[R] Detect and replace omitted data

[Sarah Goslee]

Hi Jonny,

On Tue, Oct 18, 2011 at 1:02 PM, Jonny Armstrong
<jonny5armstrong at gmail.com> wrote:
> I am analyzing the spatial distribution of fish in a stream. The stream is
> divided into equally sized units, and the number of fish in each unit is
> counted. My problem is that my dataset is missing rows where the count in a
> unit equals zero. I need to create zero data for the missing units.
>
> For example:
> day<-(c(rep(4,8),rep(6,8)))
> unit<-c(seq(1,8,1),seq(2,16,2))
> value<-floor(rnorm(16,25,10))
> x<-cbind(day,unit,value)

Thanks for the actual reproducible example.

> x
>      day unit value
>  [1,]   4    1    19
>  [2,]   4    2    15
>  [3,]   4    3    16
>  [4,]   4    4    20
>  [5,]   4    5    17
>  [6,]   4    6    15
>  [7,]   4    7    14
>  [8,]   4    8    29
>  [9,]   6    2    18
> [10,]   6    4    22
> [11,]   6    6    27
> [12,]   6    8    16
> [13,]   6   10    45
> [14,]   6   12    36
> [15,]   6   14    34
> [16,]   6   16    13
>
> Lets say the stream has 16 units. For each day, I want to fill in rows for
> any missing units (e.g., units 9-16 for day 4, the odd numbered units on day
> 6) with values of zero.

Here's one option, though it may not be terribly concise:

all.samples <- expand.grid(day=unique(x[,"day"]), unit=1:16)
all.samples <- all.samples[order(all.samples[,"day"], all.samples[,"unit"]),]
x.final <- merge(x, all.samples, all.y=TRUE)
x.final[is.na(x.final[,"value"]), "value"] <- 0

Sarah

> Does anyone know a relatively concise way to do this?
> Thank you.
>
>        [[alternative HTML version deleted]]
>

-- 
Sarah Goslee
http://www.functionaldiversity.org