[R] Plot bivariate joint pdf

Ben Bolker bolker at ufl.edu
Mon May 11 15:46:03 CEST 2009

beetle2 wrote:
> For a homework question.
> I was wondering if rcmdr has a function to plot a graph of a bivariate
> function of X and Y.
> I have a function with joint pdf
> fX,Y(x,y) = x+y for 0<x<1  , 0<y<1
> I've tried
>> x <- seq(0,1,.001) 
>> y <- seq(0,1,.001) 
>> r = x+y
>> plot(r)
> but it seems to just add them together say .2+.2 .3+.3  not other
> possibilities like
> .9 + .1

We don't do homework questions here, but a few hints:

(1) the question doesn't seem to be fully specified.  Are x and y supposed
to be uniform?

(2) you could get a reasonable representation of the solution (although
not necessarily one your prof would be happy with) by adding
runif(10000,0,1) and runif(10000,0,1)

(3) to do this analytically, think about convolutions and/or moment

  Ben Bolker

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