r – dim(X) must have a positive length when applying function in data frame
r – dim(X) must have a positive length when applying function in data frame
It happens because R coerces last_visit[,2] to a dimensionless vector, whereas apply expects the object to have some dimensions. You can prevent the coercion by adding drop=F to your command, i.e.:
apply(last_visit[,2,drop=F], 1, best_recom)
Another way would be just to use lapply or sapply on the vector:
lapply(last_visit[,2], best_recom)