# [R] Plot bivariate joint pdf

beetle2 samandbrendan at aapt.net.au
Tue May 12 00:59:03 CEST 2009

Thank you for your suggestions.
When you talked about the double itegral

did you mean solve the pdf for 1 variable by

\int \int_{0}^{1} X+y dydx

x^2/2 + x/2

Where this is a function of one variable.
Do I then plot this function ?

regards

David Winsemius wrote:
>
>
> On May 11, 2009, at 9:46 AM, 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.
>
> (4) ?integrate
> and search on "double integration".
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
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