Treats logistic for duplicates as a function of covariate z; for a given z
it computes the function at with those covariate values at a range of
distances.
     
    
    Usage
    logisticdupbyx(distance, x1, x2, models, beta, point)
 
    
    Arguments
- distance
- vector of distance values 
- x1
- covariate data for fct 1 
- x2
- covariate data for fct 2 
- models
- model list 
- beta
- logistic parameters 
- point
- TRUEfor point transect data
 
 
    
    Value
    vector of probabilities