Hello everyone! I want to calculate an instrumental variable estimator using the riv-package: riv(Y,Xex,Xend,W,method="classical") and my problem is that I either get an error because missing values are not allowed in the matrices or when I exclude NA's from the matrices it says that matrices have to be at the same length. Is there a special option how to deal with missing values when using the riv-package? Thanks to everyone how might be able to help! Jan St?rger Mannheim University