Geospatial queries

@groupby(geotable, col₁, col₂, ..., colₙ)
@groupby(geotable, [col₁, col₂, ..., colₙ])
@groupby(geotable, (col₁, col₂, ..., colₙ))

Group geospatial geotable by columns col₁, col₂, ..., colₙ.

@groupby(geotable, regex)

Group geospatial geotable by columns that match with regex.

Examples

@groupby(geotable, 1, 3, 5)
@groupby(geotable, [:a, :c, :e])
@groupby(geotable, ("a", "c", "e"))
@groupby(geotable, r"[ace]")

@transform(geotable, :col₁ = expr₁, :col₂ = expr₂, ..., :colₙ = exprₙ)

Returns geospatial geotable with columns col₁, col₂, ..., colₙ computed with expressions expr₁, expr₂, ..., exprₙ.

See also: @groupby.

Examples

@transform(geotable, :z = :x + 2*:y)
@transform(geotable, :w = :x^2 - :y^2)
@transform(geotable, :sinx = sin(:x), :cosy = cos(:y))

groups = @groupby(geotable, :y)
@transform(groups, :logx = log(:x))
@transform(groups, :expz = exp(:z))

@transform(geotable, {"z"} = {"x"} - 2*{"y"})
xnm, ynm, znm = :x, :y, :z
@transform(geotable, {znm} = {xnm} - 2*{ynm})

@combine(geotable, :col₁ = expr₁, :col₂ = expr₂, ..., :colₙ = exprₙ)

Returns geospatial geotable with columns :col₁, :col₂, ..., :colₙ computed with reduction expressions expr₁, expr₂, ..., exprₙ.

If a reduction expression is not defined for the :geometry column, the geometries will be reduced using Multi.

See also: @groupby.

Examples

@combine(geotable, :x_sum = sum(:x))
@combine(geotable, :x_mean = mean(:x))
@combine(geotable, :x_mean = mean(:x), :geometry = centroid(:geometry))

groups = @groupby(geotable, :y)
@combine(groups, :x_prod = prod(:x))
@combine(groups, :x_median = median(:x))
@combine(groups, :x_median = median(:x), :geometry = centroid(:geometry))

@combine(geotable, {"z"} = sum({"x"}) + prod({"y"}))
xnm, ynm, znm = :x, :y, :z
@combine(geotable, {znm} = sum({xnm}) + prod({ynm}))

geojoin(geotable₁, geotable₂, var₁ => agg₁, ..., varₙ => aggₙ; kind=:left, pred=intersects, on=nothing)

Joins geotable₁ with geotable₂ using a certain kind of join and predicate function pred that takes two geometries and returns a boolean ((g1, g2) -> g1 ⊆ g2).

Optionally, add a variable value match to join, in addition to geometric match, by passing a single name or list of variable names (strings or symbols) to the on keyword argument. The variable value match use the isequal function.

Whenever two or more matches are encountered, aggregate varᵢ with aggregation function aggᵢ. If no aggregation function is provided for a variable, then the aggregation function will be selected according to the scientific types: mean for continuous and first otherwise.

Kinds

• :left - Returns all rows of geotable₁ filling entries with missing when there is no match in geotable₂.
• :inner - Returns the subset of rows of geotable₁ that has a match in geotable₂.

Examples

geojoin(gtb1, gtb2)
geojoin(gtb1, gtb2, 1 => mean)
geojoin(gtb1, gtb2, :a => mean, :b => std)
geojoin(gtb1, gtb2, "a" => mean, pred=issubset)
geojoin(gtb1, gtb2, on=:a)
geojoin(gtb1, gtb2, kind=:inner, on=["a", "b"])

See also tablejoin.