On 13-Sep-09 16:47:07, czarjosh wrote: > > I am trying to learn R right now. I came from minitab and wanted > to learn something a bit more robust. I am trying to figure out > some simple probability to measures but I do not know the commands. > I am using > OSX. Are there resources for figuring out simple events? > > If I have data distributed as Normal(5,4) and I wanted to know what > the probability of P(<6) would be this, I cannot quite figute out how > to work this out.
For each of the common distributions, there is a group of R functions giving the density/point probability, the cumulative probability, the inverse of this (i.e. whiat x corresponds to a given probability), and also a function for sampling randomly from it. In the 'help' files, these four are groups togther in a single file. For the Normal distribution, these functions are dnorm pnorm qnorm rnorm So, if you enter ther command ?pnorm you will get a summary for all of them. Similarly if you enter ?pnorm or ?qnorm or ?rnorm. For your query, the probability that X < 6 is simply pnorm(q=6,mean=5,sd=4), which you can abbreviate to pnorm(6,5,4): pnorm(q=6,mean=5,sd=4) # [1] 0.5987063 pnorm(6,5,4) # [1] 0.5987063 the reason they are equaivlent as given is that when the arguments are not named, R identifies them by position, so that in "pnorm(6,5,4)" it is assumed that q=6, mean=5, sd=4. If you prefer to give them in a different order, then you will have to name them: pnorm(4,5,6) # [1] 0.4338162 pnorm(sd=4,mean=5,q=6) # [1] 0.5987063 Similarly you will find dchisq, pchisq, qchisq, rchisq for the chi-squared distribution, dt, pt, qt, rt for the Student t distribution, df, pf, qf, rf for the F distribution, dbinom etc. for the Binomial, dpois etc. for the Poisson, and many others! Hoping this helps. Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 13-Sep-09 Time: 19:59:58 ------------------------------ XFMail ------------------------------ ______________________________________________ R-help@r-project.org 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.
