zonal_statistics

zonal_statistics(GI::GItype, shapes::GDtype, fun::Function; touches=false, byfeatures=false, groupby="")

or

zonal_statistics(fun::Function, GI::GItype, shapes::GDtype; touches=false, byfeatures=false, groupby="")

or zonal_stats(...)

Compute the statistics of fun applied to the elements of the grid or image GI that lie inside the polygons of the GMTdataset shapes.

Arguments

  • GI: A grid (GMTgrid) or image (GMTimage) type uppon which the statistics will be computed by applying the fun function to the elements that fall inside the polygons of shapes.
  • shapes: A vector of GMTdataset containing the polygons inside which the elements if GI will be assigned a single value obtained by applying the function fun.
  • fun: A unidemensional function name used to compute the contant value for the GI elements that fall inside each of the polygons of shapes.

Parameters

  • touches: include all cells/pixels that are touched by the polygons. The default is to include only the cells whose centers that are inside the polygons.
  • byfeatures: Datasets read from OGR vector filres (shapes, geopackages, arrow, etc) are organized in features that may contain several geomeometries each. Each group of geometries in a Feature share the same Feauture_ID atribute. If byfeatures is true, the function fun will be applied to each feature independently. This option is actually similar to the groupby parameter but doesn’t require an attribute name. If neither of byfeatures or groupby are provided, the fun function is applied to each of the polygons independently.
  • groupby: If provided, it must be an attribute name, for example, groupby="NAME". If not provided, we use the Feature_ID attribute that is a unique identifier assigned during an OGR file reading (by the GMT6.5 C lib). If neither of byfeatures or groupby are provided, the fun function is applied to each of the polygons independently.

Examples

What is the mean altitude of Swisserland?

G = gmtread("@earth_relief_06m");
Swiss = coast(DCW=:CH, dump=true, minpts=50);
zonal_statistics(G, Swiss, mean)

1×1 GMTdataset{Float64, 2}
 Row │       X
─────┼─────────
   1 │ 1313.21

Methods

# 2 methods for generic function "zonal_statistics" from GMT:
 [1] zonal_statistics(GI::GItype, shapes::GDtype, fun::Function; touches, byfeatures, groupby)
 [2] zonal_statistics(fun::Function, GI::GItype, shapes::GDtype; touches, byfeatures, groupby)

See Also