Cross product for spray objects

Provides a natural cross product for spray objects, useful for tensors and \(k\)-forms

Usage

spraycross(S, ...)
spraycross2(S1,S2)

Arguments

S,S1,S2,...

spray objects

Details

Tensor products for sprays. This is not an algebraic product of sprays interpreted as multivariate polynomials. The function is used in the stokes package, in which vignette tensorprod() gives a use-case.

Function spraycross2() is a helper function that takes exactly two arguments. Function spraycross() is a more general function that takes any number of arguments.

Value

Returns a spray object

Author

Robin K. S. Hankin

Examples

a <- spray(matrix(1:4,2,2),c(2,5))
b <- spray(matrix(c(10,11,12,13),2,2),c(7,11))
a
#> +5*a^2*b^4 +2*a*b^3
b
#> +11*a^11*b^13 +7*a^10*b^12
spraycross2(a,b)
#> +14*a*b^3*c^10*d^12 +22*a*b^3*c^11*d^13 +35*a^2*b^4*c^10*d^12
#> +55*a^2*b^4*c^11*d^13
spraycross2(b,a)
#> +14*a^10*b^12*c*d^3 +22*a^11*b^13*c*d^3 +35*a^10*b^12*c^2*d^4
#> +55*a^11*b^13*c^2*d^4

spraycross(a,b,b)
#> +242*a*b^3*c^11*d^13*e^11*f^13 +605*a^2*b^4*c^11*d^13*e^11*f^13
#> +154*a*b^3*c^10*d^12*e^11*f^13 +385*a^2*b^4*c^10*d^12*e^11*f^13
#> +154*a*b^3*c^11*d^13*e^10*f^12 +385*a^2*b^4*c^11*d^13*e^10*f^12
#> +98*a*b^3*c^10*d^12*e^10*f^12 +245*a^2*b^4*c^10*d^12*e^10*f^12