These predicate functions checks for whether a geometry varies along a given
axis. While it is common in 2 dimensions to ask whether something is vertical
or horizontal that notion does not scale well to 3 dimensions and euclid
instead elects to check for whether a given geometry is constant in a
specific coordinate value. As such, e.g.
has_constant_x() is equivalent to
asking whether a given 2 dimensional geometry is vertical but also works for
3 dimensional geometries.
is_constant_in(x, axis) has_constant_x(x) has_constant_y(x) has_constant_z(x)
A geometry vector
One or more specifications of the axes to check against as
A logical vector
# Check for horizontal vector v <- vec(1, -2:2) has_constant_y(v)#>  FALSE FALSE TRUE FALSE FALSE#>  FALSE TRUE FALSE