find_limit_star: Find the limits of a Stars density distributions

In JohMast/UrbanStars: Extract Statistics of Urban Centers

Description

Find the limits of a Stars density distributions

Usage

find_limit_star(Star, UrbanLayerName, Threshold = 50,
  SlopeThreshold = 0.01, SlopeWindow = 3)

Arguments

Star	a Star object that contains columns "BeamId" and "SegmentId", as created by create_star()
UrbanLayerName	the name of the column which holds the density values
Threshold	a threshold under which the density is considered nonurban
SlopeThreshold	the threshold under which the in SlopeWindow calculated mean of the slope is considered to be small
SlopeWindow	a forward looking search window in which the mean slope is evaluated

Details

Splits the dataframe of a Star into its constituent beams (identified by their "BeamId"). Each beams UrbanLayerName column is then evaluated to find a plausible segmentation point, which can be considered the urban limit. The criterium for the point being: First point at which

1. the value is lower than "Threshold" and

2. the mean slope over the next SlopeWindow data points is lower than SlopeThreshold

The limits are then used to create a logical vector of length(Star), indicating for each segment of the Star whether it is urban. If for at least one of the beams, no point satisfies both conditions, NA is returned.

Value

Logical vector

Author(s)

Johannes Mast

See Also

find_limit, split_star_into_beams

Examples

find_limit_star(Star,UrbanLayerName,Threshold=50,SlopeThreshold=0.01,SlopeWindow=3)

JohMast/UrbanStars documentation built on May 28, 2019, 8:58 p.m.