spatialEco (version 0.1-5)

sample.line: Systematic or random point sample of line(s)

Description

Creates a systematic or random point sample of an sp SpatialLinesDataFrame object based on distance spacing, fixed size or proportional size

Usage

sample.line(x, d = 100, p = NULL, n = NULL, type = "regular", longlat = FALSE, min.samp = 1, ...)

Arguments

x

sp class SpatialLinesDataFrame object

d

Sample distance. For regular sample.

p

Proportional sample size (length * p), expected value is 0-1. For regular or random.

n

Fixed sample size. For regular or random

type

Defines sample type. Options are "regular" or "random". A regular sample results in a systematic, evenly spaced sample.

longlat

TRUE/FALSE is data in geographic units, if TRUE distance is in kilometres

min.samp

Minimal number of sample points for a given line (default is 1 point)

...

Additional argument passed to spsample

Value

sp SpatialPointsDataFrame object.

Examples

 require(sp)
 sp.lines <- SpatialLines(list(Lines(list(Line(cbind(c(1,2,3),c(3,2,2)))), ID="1"),
                          Lines(list(Line(cbind(c(1,2,3),c(1,1.5,1)))), ID="2")))
 sp.lines <- SpatialLinesDataFrame( sp.lines, data.frame(ID=1:2, row.names=c(1,2)) )

par(mfrow=c(2,2))
 # Create systematic sample at 20 km spacing 
 reg.sample <- sample.line(sp.lines, d = 20, type = "regular", longlat = TRUE)
   plot(sp.lines)
     plot(reg.sample, pch = 20, add = TRUE)
  box()
  title("systematic d = 20")

 # Create fixed size (n = 20) systematic sample
 reg.sample <- sample.line(sp.lines, n = 20, type = "regular", longlat = TRUE)  
   plot(sp.lines)
     plot(reg.sample, pch = 20, add = TRUE)
     box()
  title("systematic n = 20")
  
 # Create fixed size (n = 20) random sample 
 rand.sample <- sample.line(sp.lines, n = 20, type = "random", longlat = TRUE)  
   plot(sp.lines)
     plot(rand.sample, pch = 20, add = TRUE)
     box()	  
     title("rand n = 20")
  
 # Create proportional (p = 0.10) random sample
 rand.sample <- sample.line(sp.lines, p = 0.10, type = "random", longlat = TRUE)  
   plot(sp.lines)
     plot(rand.sample, pch = 20, add = TRUE)
     box()
  title("rand p = 0.10")