I'm trying to figure out exactly what the prob parameter in the sample
function does.
With the following code, does sample look randomly for the first
possible sample--let's say it choses the second element--and then
assess whether it can be chosen according to it's probability which is
0.8? It seems unlikely it would work like this.
Or does it create a `biased die' which in this case would have ten
sides that each come up according to the probabilities in myProb, and
roll it to see which is the first element chosen, then remove that
element, create a new biased die with 9 sides and roll it again?
i <- c(1:10)
myProbs <- c(0.2, 0.8, 0.3, 0.2, 0.1, 0.1, 0.1, 0.2, 0.3, 0.4)
f <- sample(i,5, replace=FALSE, prob=myProbs)
Then what's the difference in terms of sampling between the following
two examples, the second of which has been created so that the
probabilities add to 1?
i <- c(1:10)
myProbs <- c(0.1, 0.1, 0.1, 0.1, 0.1, 0.9, 0.9, 0.9, 0.9, 0.9)
f <- sample(i,5, replace=FALSE, prob=myProbs)
i <- c(1:10)
myProbs <- c(0.1/5, 0.1/5, 0.1/5, 0.1/5, 0.1/5, 0.9/5, 0.9/5, 0.9/5,
0.9/5, 0.9/5)
f <- sample(i,5, replace=FALSE, prob=myProbs)
Thank you,
Thomas Chesney
This message and any attachment are intended solely for the addressee and may
contain confidential information. If you have received this message in error,
please send it back to me, and immediately delete it. Please do not use, copy
or disclose the information contained in this message or in any attachment.
Any views or opinions expressed by the author of this email do not necessarily
reflect the views of the University of Nottingham.
This message has been checked for viruses but the contents of an attachment
may still contain software viruses which could damage your computer system, you
are advised to perform your own checks. Email communications with the
University of Nottingham may be monitored as permitted by UK legislation.
______________________________________________
[email protected] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
