# [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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```

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