engine_K2d_sph: Engine for computing K-function
In adchSTATS/spatstatspacesphereadd: Additions to spatstat

Engine for calculating K-function of point processes on the product space of R^(2, 3) and S^(1, 2).

1	engine_K2d_sph(r, s, x_vec, y_vec, dists_sph, Dmat)

`r`	Vector of values for the argument r at which K(r, s) should be evaluated.
`s`	Vector of values for the argument s at which K(r, s) should be evaluated.
`x_vec`	Vector of x coordinates.
`y_vec`	Vector of y coordinates.
`dists_sph`	Matrix of distances between points on S^2.
`Dmat`	Matrix of all possible values to sum over to. The values of the K-function before multiplying by the indicator function. Constants may be multiplied on the resulting matrix.