Rdistance (version 1.3.2)

perp.dists: Compute off-transect distances from sighting distances and angles

Description

Computes off-transect (also called 'perpendicular') distances from measures of sighting distance and sighting angle.

Usage

perp.dists(obs.dist, obs.angle, digits=1)

Arguments

obs.dist

Vector (e.g., a column of a data.frame) that contains the observed or sighting distances from the observer to the detected objects.

obs.angle

Vector (e.g., a column of a data.frame) that contains the observed or sighting angles from the line transect to the detected objects. Angles must be measured in degrees.

digits

Scalar number of digits to round output distances to.

Value

A vector of off-transect (or perpendicular) distances. Units are the same as obs.dist.

Details

If observers recorded sighting distance and sighting angle (as is often common in line transect surveys), use this function to convert to off-transect distances, the required input data for F.dfunc.estim.

References

Buckland, S.T., Anderson, D.R., Burnham, K.P. and Laake, J.L. 1993. Distance Sampling: Estimating Abundance of Biological Populations. Chapman and Hall, London.

See Also

F.dfunc.estim

Examples

# NOT RUN {
# Load the example dataset of sparrow detections from package
data(sparrow.detections)

# Compute perpendicular, off-transect distances from the observer's sight distance and angle
sparrow.detections$dist <- perp.dists(obs.dist=sparrow.detections$sightdist,
                                  obs.angle=sparrow.detections$sightangle)

# Proceed to fitting the detection function with F.dfunc.estim
# }