R/qprod.R

In aaronolsen/linkR: 3D Lever and Linkage Mechanism Modeling

qprod <- function(a, b){
	
	## Product of two quaternions
	q <- c(
		b[1]*a[1] - b[2]*a[2] - b[3]*a[3] - b[4]*a[4],
		b[1]*a[2] + b[2]*a[1] - b[3]*a[4] + b[4]*a[3],
		b[1]*a[3] + b[2]*a[4] + b[3]*a[1] - b[4]*a[2],
		b[1]*a[4] - b[2]*a[3] + b[3]*a[2] + b[4]*a[1]
	)
}