corridor: Corridor

In move: Visualizing and Analyzing Animal Track Data

Description

Corridor identifies movement track segments whose attributes suggest corridor use behavior

Usage

  ## S4 method for signature '.MoveTrackSingle'
corridor(x,speedProp=.75, circProp=.25, plot=FALSE, ...)
  ## S4 method for signature '.MoveTrackStack'
corridor(x,speedProp=.75, circProp=.25, plot=FALSE, ...)

Arguments

x	Move or MoveStack
speedProp	numeric between 0 and 1, defines the proportion of speeds which are high enough to be a valid corridor point
circProp	numeric between 0 and 1, defines the proportion of trajectories that are low enough to be a valid corridor point
plot	logical, if TRUE the track is plotted together with dots that indicate corridor points (color scale indicates how many corridor points are near by, less: blue, many: pink)
...	additional arguments like levels and nlevels, see details

Details

The corridor function uses the attributes of a movement step to identify movement steps that exhibit corridor use behavior. For each segment, the speed and the azimuth are calculated and assigned to the segment midpoint. A circular buffer is created around the midpoint of each segment whose radius is equal to half the segment length. The segment azimuth (180 >= azimuth > -180) is then converted into a new unit (the 'pseudo-azimuth' 0 <= 360). Subsequent, the circular variance of the pseudo-azimuths of all segment midpoints that fall within the circular buffer are calculated. This identifies segments that are near parallel segments. Next, it is determined whether a segment's speed is higher than speedProp (by default the upper 25% speeds) and its circular variance is lower than circProp (by default the lower 25% of all variances). Segment midpoints that meet both of these requirements are considered as a 'corridor' point, all others are considered 'non-corridor' points. Finally, a corridor point is determined to be within a true corridor if within its buffer there are more 'corridor' points than 'non-corridor' points.

Value

The function returns a MoveBurst object or a list of MoveBurst objects (if a MoveStack is supplied). The MoveBurst dateframe stores the following information:
- segment midpoint
- speed
- azimuth
- pseudo-azimuth
- circular variance

The object is bursted by the factor that indicates whether a coordinate belongs to a corridor segment or not.

Note

The default values for the speedProp and circProp can be changed as per the users discretion using the according argument. If the result of the function is assigned to a variable a MoveBurst object is returned (see Value).

Author(s)

Marco Smolla

References

LaPoint, S., Gallery, P., Wikelski, M. and Kays, R. (2013), Animal Behavior, Cost-based Corridor Models, and Real Corridors. Landscape Ecology. doi:10.1007/s10980-013-9910-0.

Examples

data(leroy)  
  tmp <- corridor(leroy, plot=TRUE)
  head(tmp) #if assigned to a variable, the coordinates are exported
  data(fishers)
  stacktmp <- corridor(fishers[c(1:400,sum(n.locs(fishers))-(400:1)),]) #working with a stack

move documentation built on Jan. 16, 2017, 2:22 a.m.