The Voronoi measure of Stevens and Olsen (2004): every unit of the frame is assigned to its nearest sampled unit, the inclusion probabilities assigned to each sampled unit are summed, and the balance is the mean squared deviation of those sums from one. Zero is perfect balance; simple random samples give values near one. With strata the measure is computed within each stratum and pooled.
Arguments
- sample
A
select_units()sample.- by_stratum
Return one value per stratum instead of the pooled one.
References
Stevens, D. L. and Olsen, A. R. (2004). Spatially balanced sampling of natural resources. Journal of the American Statistical Association, 99, 262-278.
Examples
cells <- expand.grid(x = 1:10, y = 1:10)
spatial_balance(select_units(cells, n = 10, method = "lpm", seed = 1))
#> [1] 0.128
spatial_balance(select_units(cells, n = 10, method = "srs", seed = 1))
#> [1] 0.268