Checks whether the input dissimilarity matrix is metric (i.e. all triplets fulfill the triangle inequality).
     
    
    Usage
    is.metric(x, tol = 1e-04)
 
    
    Arguments
- x
- Either an object of class - trajectories,  a symmetric- matrixor an object of class- distcontaining the distance values between pairs of ecological states.
 
- tol
- Tolerance value for metricity 
 
    
    Value
    A boolean indicating metric property
     
    
    Author
    Miquel De Cáceres, CREAF