This function creates a probability (stochastic) grid 
        for trajectory model data based on settlement location, 
        normalized by run.
        
        probability_grid = compute_probability_settle([myfile1.nc, myfile2.nc],
                                               bbox = [-75, 23, -60, 45],
                                               nx = 1000, ny = 1000,
                                               method='overall')

def compute_probability_settle(trajectory_files, bbox=None, 
                        nx=1000, ny=1000, method='overall'):
    """
        This function creates a probability (stochastic) grid 
        for trajectory model data based on settlement location, 
        normalized by run.
        
        probability_grid = compute_probability_settle([myfile1.nc, myfile2.nc],
                                               bbox = [-75, 23, -60, 45],
                                               nx = 1000, ny = 1000,
                                               method='overall')  
    """
    prob = compute_probability(trajectory_files,
                               bbox,
                               nx, ny,
                               method,
                               parameter='settlement',
                              )
    return prob