[R] Plot bivariate joint pdf

beetle2 samandbrendan at aapt.net.au
Thu May 14 03:56:52 CEST 2009


Hi All,
Thankyou for your sugestions,
I Look through some other posts and learnt about the
persp() function.

So I ended up using;

x <- seq(0, 1, len = 20)
y <- seq(0, 1, len = 20)

model = function (x, y){
x+y}
z=outer(x, y ,model);

persp(x,y,z,theta=30,phi=30,ticktype="detailed")

Worked a real treat.

Thankyou all




Ben Bolker wrote:
> 
> 
> 
> 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
> generating
> functions.
> 
>   Ben Bolker
> 
> 

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