[R] rmultinomial() function

Mary Black mhbridge at usc.edu
Tue Mar 18 23:28:47 CET 2008


After scouring the online R resources and help pages, I still need clarification on the function rmultinomial().  I would like to create a vector, say of 100 elements, where every element in the vector can take on the value of 0, 1 or 2, and where each of those values have a specific probability. ie. the probability a given element in the vector = 0 is 0.06, 1 = 0.38, 2 = 0.56 (probabilities sum to 1). Can I use rmultinomial() function to do this?  

The following code does not seem to produce the result I need, but this sort of code is all I could find the R "help" pages:
 
> rmultinomial(100,c(0.06,0.38,0.56))
[1]  3 29 68
> rmultinomial(100,c(0.06,0.38,0.56),long=TRUE)
  [1] 3 3 2 2 3 2 3 3 2 3 2 3 3 3 2 2 3 3 2 3 1 2 3 3 3 3 3 3 2 3 3 2 3 3 3 2 3 2 2 3 2 3 2 3 3 3 2 1 3 3 1
 [52] 2 3 2 2 3 3 2 2 2 1 3 3 2 3 3 3 3 2 3 3 3 3 2 3 2 3 3 2 3 3 2 3 3 2 3 2 3 3 2 3 3 3 2 3 2 2 2 2 2

Also, I don't really understand the difference between the default long=FALSE and long=TRUE.  The R "help" simply states that you use "long TRUE to choose one generator, FALSE to choose another one"; however I could not find any documentation that described what the difference between those generators is.  Any clarification would be greatly appreciated! 

Thanks,

Mary



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