This function creates a new column in data which contains the estimated
number of animals for each detection. This is the number of observed individuals
divided by their probability of detection using MCDS methods (size/detection probability).
In the case that no size column is given in dis.data, it is assumed that
detections were made of individuals and size is set to 1 for all detections. The values
for size and NHAT are set to zero in case the distance was larger than the
truncation distance w specified in det.fct.object.
In addition, a new column area is created which is used as the offset in the
second stage count model (segment length * (truncation distance/1000) * 2). The truncation
distance is divided by 1000 to convert it from metres to km. It is assumed that the
segment data represents two-sided surveys. In case the survey was one-sided, this column needs to
be divided by 2 after the call to this function.
Arguments
- data
distance data object used with
det.fctto estimate probabilities of detection- ddf.obj
detection function object created by
ddf
Examples
data(dis.data.re)
result<-ddf(dsmodel=~mcds(key="hn", formula=~1), data=dis.data.re,method="ds",
meta.data= list(width=250,binned=FALSE))
#> Error in ddf(dsmodel = ~mcds(key = "hn", formula = ~1), data = dis.data.re, method = "ds", meta.data = list(width = 250, binned = FALSE)): could not find function "ddf"
dis.data<-create.NHAT(dis.data.re,result)
#> Error in which(data$distance <= ddf.obj$meta.data$width): object 'result' not found