[R] p-value calculation on a joint distribution

[Leon Yee]

Dear R users,

     For a uni-variable distribution represented in a numerical vector, 
we can obtain a distribution function using 'ecdf', and then calculate 
corresponding p-values. But if I have a 2-column dataframe representing 
a bi-variable joint distribution, given a pair of values, how can I get 
the p-value? And how can I plot out the density of the joint distribution?

Best wishes,

Leon