Given a sample of exceedances, compute the moment estimator of the real shape parameter.
     
    
    
    Arguments
- xdat
- vector of positive observations of length \(n\) 
- k
- number of largest order statistics 
 
    
    Value
    a data frame with the number of order statistics k and the shape parameter estimate shape, or a single numeric value if k is a scalar.
     
    
    References
    Dekkers, A.L.M. and de Haan, L. (1989). On the estimation of the extreme-value index and large quantile estimation., Annals of Statistics, 17, 1795-1833.