Hallo
I am teaching a very elementary intro course about R, and want to show
the students how to find the distribution of the maximum of rolling
two balanced die. Is there perhaps a more elegant way to do this,
other than the way I am using below? (I would like to show them two
ways - the one shown here, and perhaps and improved/elegant approach
(showing off the "beauty" of R.
My code is as follows:
R> n <- 20000
R> d1 <- sample(1:6, n, replace=TRUE)
R> d2 <- sample(1:6, n, replace=TRUE)
R> d <- apply(matrix(c(d1,d2), nrow=n, byrow=TRUE), 1, max)
R> round(table(d)/n, 3)
d
1 2 3 4 5 6
0.030 0.084 0.137 0.195 0.246 0.308
Why not d <- ifelse( d1 > d2, d1, d2 ) or d <- pmax( d1, d2 ) ? Apply operations may seem "beautiful", but I think the speed and simplicity of vectorized operations are truly beautiful. --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnewmil@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity. Jaap van Wyk <J.vanWyk@ru.ac.za> wrote: Hallo I am teaching a very elementary intro course about R, and want to show the students how to find the distribution of the maximum of rolling two balanced die. Is there perhaps a more elegant way to do this, other than the way I am using below? (I would like to show them two ways - the one shown here, and perhaps and improved/elegant approach (showing off the "beauty" of R. My code is as follows: R> n <- 20000 R> d1 <- sample(1:6, n, replace=TRUE) R> d2 <- sample(1:6, n, replace=TRUE) R> d <- apply(matrix(c(d1,d2), nrow=n, byrow=TRUE), 1, max) R> round(table(d)/n, 3) d 1 2 3 4 5 6 0.030 0.084 0.137 0.195 0.246 0.308 _____________________________________________ 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. [[alternative HTML version deleted]]
> -----Original Message----- > From: r-help-bounces at r-project.org > [mailto:r-help-bounces at r-project.org] On Behalf Of Jaap van Wyk > Sent: 30 August 2011 04:57 > To: r-help at r-project.org > Subject: [R] Simulating distribution of max of two die > > how to find the distribution of the > maximum of rolling two balanced die. Is there perhaps a more > elegant way to do this, other than the way I am using below?#Perhaps dice <- matrix(sample(1:6, 40000,replace=T), ncol=2) dice.max <- apply(dice, 1, max) barplot(table(dice.max)) #and just for interest mids<-barplot(table(dice.max)/length(dice.max)) #gives proportions all.pairs <- expand.grid(1:6, 1:6) dice.max.exact <- apply(all.pairs, 1, max) points(mids, table(dice.max.exact)/36, pch="_", cex=2, col=2) ******************************************************************* This email and any attachments are confidential. Any use...{{dropped:8}}
For this example you can work out every possibility, you can use this in place (or in addition to) the simulations. Here is a quick example with a couple other ways to look at what is happening: all.rolls <- expand.grid(1:6,1:6) max.roll <- apply(all.rolls, 1, max) round(prop.table(table(max.roll)),3) library(MASS) fractions( prop.table(table(max.roll))) print( paste(table(max.roll),'/36',sep=''), quote=FALSE ) library(TeachingDemos) plot.dice( expand.grid(1:6,1:6), layout=c(6,6) ) -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.snow at imail.org 801.408.8111> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- > project.org] On Behalf Of Jaap van Wyk > Sent: Monday, August 29, 2011 9:57 PM > To: r-help at r-project.org > Subject: [R] Simulating distribution of max of two die > > Hallo > > I am teaching a very elementary intro course about R, and want to show > the students how to find the distribution of the maximum of rolling > two balanced die. Is there perhaps a more elegant way to do this, > other than the way I am using below? (I would like to show them two > ways - the one shown here, and perhaps and improved/elegant approach > (showing off the "beauty" of R. > My code is as follows: > > R> n <- 20000 > R> d1 <- sample(1:6, n, replace=TRUE) > R> d2 <- sample(1:6, n, replace=TRUE) > R> d <- apply(matrix(c(d1,d2), nrow=n, byrow=TRUE), 1, max) > R> round(table(d)/n, 3) > d > 1 2 3 4 5 6 > 0.030 0.084 0.137 0.195 0.246 0.308 > > ______________________________________________ > R-help at 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.