Thanks Ben and Eric. I've already tried rmultinom(), and there is a
rmultinomial() function as well (which is in the multinomRob package). The
rmultinomial() is supposed to be a random number generator for the multinomial
distribution. There is an argument long which if set to TRUE or FALSE,
utlize different generators, but the documentation doesn't explain any further.
Thus, my confusion about the output. If anyone can explain further how the two
generators are different, I would love to know!
- Original Message -
From: Ben Fairbank [EMAIL PROTECTED]
Date: Wednesday, March 19, 2008 7:36 am
Subject: RE: [PS] [R] rmultinomial() function
To: Mary Black [EMAIL PROTECTED], r-help@r-project.org
Mary --
The dmultinomial function (try ?Multinomial, noting that it is an
uppercase M) has a log option, which, if set to TRUE, returns
logarithms of
probabilities, but that is for computing probabilities, not generating
samples. Perhaps the long you referred to is a misprint for log?
In any case, try ?Multinomial, and give rmultinom() another try.
Note,however, that its output gives the _number_ of each of the
sampled items
produced in a single sample, not the sequence of draws. If you
need the
sequence, then I think that the reply from Erik Iverson tells you how
best to proceed.
Ben
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
project.org]On Behalf Of Mary Black
Sent: Tuesday, March 18, 2008 5:29 PM
To: r-help@r-project.org
Subject: [PS] [R] rmultinomial() function
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
takeon 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
thissort 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
longTRUE 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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