spatialEco (version 2.0-1)

optimized.sample.variance: Optimized sample variance

Description

Draws an optimal sample that minimizes or maximizes the sample variance

Usage

optimized.sample.variance(x, n, type = "maximized")

Value

A data.frame with "idx" representing the index of the original vector and "y" is the value of the sampled data

Arguments

x

A vector to draw a sample from

n

Number of samples to draw

type

Type of sample variance optimization c("maximized", "minimized")

Author

Jeffrey S. Evans <[e-mail]>

Examples

library(sf)
data(meuse, package = "sp")
meuse <- st_as_sf(meuse, coords = c("x", "y"), crs = 28992, 
                  agr = "constant")

 n = 15
 # Draw n samples that maximize the variance of y
 ( max.sv <- optimized.sample.variance(meuse$zinc, 15) )
 
 # Draw n samples that minimize the variance of y
 ( min.sv <- optimized.sample.variance(meuse$zinc, 15, 
               type="minimized") )
 
 # Plot results
 plot(st_geometry(meuse), pch=19, col="grey")
   plot(st_geometry(meuse[max.sv$idx,]), col="red", add=TRUE, pch=19)
     plot(st_geometry(meuse[min.sv$idx,]), col="blue", add=TRUE, pch=19)
 	  box()
     legend("topleft", legend=c("population","maximized variance", 
            "minimized variance"), col=c("grey","red","blue"),  
            pch=c(19,19,19))