...: additional arguments to lower level functions
value: Vector of variables or formula specifying which nodes to remove
Examples
m <- lvm()addvar(m)<-~y1+y2+x
covariance(m)<- y1~y2
regression(m)<- c(y1,y2)~ x
### Cancel the covariance between the residuals of y1 and y2cancel(m)<- y1~y2
### Remove y2 from the modelrmvar(m)<-~y2