Celine,
The posting guide directs you to "Use an informative subject line (not
something like `question')". Doing so will increase the probability of
getting an informative response.
You need to spend a more time with the help pages and with "An
Introduction to R".
--
Specifically for the help page
?Logic
you needed to know that "The longer form evaluates left to right examining
only the first element of each vector" (referring to the behavior of
"&&"), which I suspect is much different than you assumed.
As for this help page:
?rmultinom
Using rmultinom( 1 , 1, p) %% 2 suggests you didn't understand the
returned value.
--
For "An Introduction to R" see section 5.1 where it explains what it means
to order the elements of a matrix in "column major order"
For example, using your construction of the matrix 'p':
as.vector( p )
[1] 0.07692308 0.23076923 0.07692308 0.15384615 0.15384615 0.30769231
is probably not what you expected.
--
Ordinarily, you might benefit from following the advice of the posting
guide, which you are asked to consult before posting. However, I see that
the suggestion there to
* Do help.search("keyword") "
Fails miserably when I tried
help.search("sample")
to direct me to the function named 'sample', which I think solves your
problem, which I guess is to return the row and column location of the '1'
in a multinomial sample from a two-way table of probabilities with N = 1.
If my guess was correct, then you want something like this:
which(array(seq(along=p),dim(p))==sample(length(p),1,prob=p), arr.ind=TRUE)
row col
[1,] 2 1
see
?which
?sample
?seq
for further details.
HTH,
Chuck
On Sat, 18 Nov 2006, David Barron wrote:
I'm not sure what the last line is trying to achieve, but this might
be what you want:
i <- ifelse(m==0, l/ky, l/ky + 1)
j <- ifelse(m==0,ky, l %% ky)
On 18/11/06, C?line Henzelin <[EMAIL PROTECTED]> wrote:
Hello,
I need help to understand my error in this code... I would like to make a
direct sampler...
thanks
Celine
p<-matrix(c(1,2,3,2,1,4),3,2,byrow=T)
p<-p/sum(p)
ky<-ncol(p)
kx<-nrow(p)
p.vec<-as.vector(t(p))
l<-rmultinom(1,1,p)
l<-(t(l))
m<-(l%%ky)
ifelse (m==0, i<-l/ky && (j<-ky), i<-((l/ky)+1) && (j<-(l %% ky)
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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--
=================================
David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP
______________________________________________
R-help@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://biostat.ucsd.edu/~cberry/ La Jolla, San Diego 92093-0717
______________________________________________
R-help@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
