estimateN  R Documentation 
Estimate abundance given a distance function,
a "merged" data frame containing detections and transect lengths, area,
and the number of sides surveyed (if linetransects).
This is called internally by abundEstim
. Most users will call
abundEstim
to estimate abundance.
estimateN(
dfunc,
data,
area = NULL,
surveyedSides,
lengthColumn,
control = RdistanceControls()
)
dfunc 
An estimate distance function (see 
data 
A data frame containing distance observations, transects,
and lengths. This data frame must have a column named 'siteID' that identifies
unique sites (transects or points). If observations were made on linetransects, this
data frame must also have a column named
by the 
area 
A scalar containing the total area of
inference. Commonly, this is study area size.
If 
surveyedSides 
The number of sides of the transect that were surveyed. Either 1 or 2. Only applies to line transects. 
lengthColumn 
Character string specifying the (single) column in

control 
A list containing optimization control parameters such
as the maximum number of iterations, tolerance, the optimizer to use,
etc. See the

The abundance estimate for linetransect surveys (if no covariates are included in the detection function and both sides of the transect were observed) is
N =\frac{n(A)}{2(ESW)(L)}
where n is total number of sighted individuals
(i.e., sum(dfunc$detections$groupSizes)
), L is the total length of
surveyed transect (i.e., sum(siteData[,lengthColumn])
),
and ESW is effective strip width
computed from the estimated distance function (i.e., ESW(dfunc)
).
If only one side of transects were observed, the "2" in the denominator
is not present (or, replaced with a "1").
The abundance estimate for point transect surveys (if no covariates are included) is
N =\frac{n(A)}{\pi(ESR^2)(P)}
where n is total number of sighted individuals,
P is the total number of surveyed points,
and ESR is effective search radius
computed from the estimated distance function (i.e., ESR(dfunc)
).
Setting plot.bs=FALSE
and showProgress=FALSE
suppresses all intermediate output.
A list containing the following components:
density 
Estimated density in the surveyed area. 
abundance 
Estimated abundance on the study area. 
n.groups 
The number of detections (not individuals, unless all group sizes = 1) used to estimate density and abundance. 
n.seen 
The number of individuals (sum of group sizes) used to estimate density and abundance. 
area 
Total area of inference. Study area size 
surveyedUnits 
Number of surveyed sites. This is total transect length for linetransects and number of points for pointtransects. This total transect length does not include NA transects. 
surveyedSides 
Number of sides (1 or 2) of transects surveyed. Only relevant for linetransects. 
avg.group.size 
Average group size on nonNA transects 
w 
Strip width. 
pDetection 
Probability of detection. 
For linetransects that do not involve covariates, x$density is x$n.seen / (x$surveyedSides * x$w * x$pDetection * x$surveyedUnits)
dfuncEstim
, abundEstim
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