Calculate an empirical groundwater-head variogram — ps

Calculates an ordinary or residual empirical variogram without fitting a covariance model. Directions follow the gstat convention: degrees clockwise from positive Y (North), periodic over 180 degrees. Pair counts and projected coordinate units are retained.

Usage

ps_variogram(
  points,
  formula = Z ~ 1,
  cutoff = NULL,
  width = NULL,
  boundaries = NULL,
  directions = 0,
  direction_tolerance = NULL,
  robust = FALSE,
  cloud = FALSE
)

Arguments

points: Groundwater-head points with a Z column.
formula: Head/trend formula, such as Z ~ 1 or Z ~ elevation.
cutoff: Maximum pair distance.
width: Positive lag width.
boundaries: Optional strictly increasing lag upper boundaries.
directions: Direction angles clockwise from North.
direction_tolerance: Horizontal tolerance in degrees.
robust: Use gstat's Cressie robust estimator.
cloud: Return individual pair semivariances.

Value

A potentiomap_variogram with empirical values, formula, directions, point summary, settings and conditions.

References

Pebesma (2004), doi:10.1016/j.cageo.2004.03.012 .

Examples

data("synthetic_wells")
pts <- ps_make_points(synthetic_wells, "x", "y", "gw_elevation",
                      "well_id", "EPSG:26916")
v <- ps_variogram(pts, cutoff = 3000, width = 300)
head(v$empirical)
#>   np      dist     gamma dir.hor dir.ver   id
#> 1 15  175.0445 0.0744700       0       0 var1
#> 2 47  456.9771 0.5025138       0       0 var1
#> 3 53  751.7839 1.2764792       0       0 var1
#> 4 62 1037.5377 1.9806565       0       0 var1
#> 5 72 1362.8381 3.4161986       0       0 var1
#> 6 74 1649.0900 4.4004966       0       0 var1
# An empirical variogram does not establish one correct covariance model.