On Oct 18, 2011, at 2:24 PM, Sarah Goslee wrote:
Hi Jonny,
On Tue, Oct 18, 2011 at 1:02 PM, Jonny Armstrong
<jonny5armstr...@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.
I could not figure out what you wanted precisely. If "day" is the row
designator, and you want values by 'unit' and 'day' with zeros for the
missing, then that is exactly what `xtab` delivers:
> xtabs(value ~ day+unit, data=x)
unit
day 1 2 3 4 5 6 7 8 10 12 14 16
4 25 34 3 25 38 18 19 33 0 0 0 0
6 0 22 0 42 0 37 0 4 12 31 17 28
You cannot get much more concise than that.
--
david.
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
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David Winsemius, MD
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
