It might help if you write your function as follows:
f <- function(x,y ,n, pa, pb) (factorial(n)/
(factorial(x) * factorial(y) * factorial(n-x-y))*
pa^x * pb^y * ((1-pa-pb)^(n-x-y)))I hope this fills in enough gaps that you will be able to complete the remaining steps.
Good luck. spencer graves
Sun wrote:
Hi, Rusers:
Thanks for answering my last questions. I am frustrated in plotting a trinomial pmf function
f(x,y | n, pa, pb) = factorial(n)/ (factorial(x) * factorial(y) * factorial (n-x-y))* pa^x * pb^y * ((1-pa-pb)^(n-x-y))
obviously it is a bivariate function of x and y. But I have put a lot of time on this.
********************************** x <- seq(0, n, len = n/2+1) # for now I set it to n/2 to control x+y <= n y <- seq(0, n, len = n/2+1) f = factorial(n)/ (factorial(x) * factorial(y) * factorial (n-x-y))* pa^x * pb^y * ((1-pa-pb)^(n-x-y)) wireframe(f ~ x * y, shade = TRUE) **********************************
well, but it plots nothing out.
I wonder if you could help me? Seems R is hard to learn without your help.
Many thanks,
Sun [[alternative HTML version deleted]]
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