Re: [R] A Maze Generator

From: Clint Bowman <clint_at_ecy.wa.gov>
Date: Tue, 29 Apr 2008 14:49:48 -0700 (PDT)

I'm familiar with mazes that have a designated starting and ending points but don't see any here (or is this just a maze

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On Tue, 29 Apr 2008, McGehee, Robert wrote:

> Thanks! I wasn't on a clean R session so I didn't catch this. I intended the 'i' to be the same from the last for loop, but as you point out on the first run there is no 'i'!
>
> Try this:
>
> plotMaze <- function(z, text=FALSE, lwd=2, ...) {
> N <- nrow(z)
> y <- -matrix(rep(1:N, N), N, N, byrow=FALSE)-1
> x <- matrix(rep(1:N, N), N, N, byrow=TRUE)
> plot(1:(N+1), -1:-(N+1), type="n", ylab="", xlab="", axes=FALSE, ...)
> segments(1, -1:-(N+1) , N+1, -1:-(N+1), lwd=lwd)
> segments(1:(N+1), -1, 1:(N+1), -(N+1), lwd=lwd)
> segments(x+(z==4), y+(z==3), x+(z!=2), y+(z!=1), col="white", lwd=lwd)
> if (text) text(x+0.5, y+0.5, z)
> rect(1, -1, N+1, -(N+1), lwd=lwd)
> }
>
>
> makeMaze <- function(N, p=1) {
> z <- matrix(NA+0, N, N)
> s <- function(x) if (length(x)==1) x else sample(x, size=1)
> z[s(1:length(z))] <- 0
> i <- 1
> while (any(is.na(z))) {
> xx <- list(z[c(2:N, N),],
> z[,c(1, 1:(N-1))],
> z[c(1, 1:(N-1)),],
> z[,c(2:N, N)])
> xx[[1]][N,] <- NA; xx[[2]][,1] <- NA; xx[[3]][1,] <- NA; xx[[4]][,N] <- NA
> prb <- rep(1, 4); prb[i] <- p
> for (i in sample(1:4, prob=prb)) {
> q <- !is.na(xx[[i]]) & is.na(z)
> if (!any(q)) next
> z[s(which(q))] <- i
> break
> }
> }
> z
> }
> set.seed(1)
> plotMaze(makeMaze(10), main="Simple Maze")
> plotMaze(makeMaze(25), main="Hard Maze", lwd=1)
>
>
> -----Original Message-----
> From: Peter Dalgaard [mailto:p.dalgaard_at_biostat.ku.dk]
> Sent: Tuesday, April 29, 2008 5:34 PM
> To: McGehee, Robert
> Cc: r-help
> Subject: Re: [R] A Maze Generator
>
> McGehee, Robert wrote:
> > I had some fun this afternoon coding up a 'maze generator' in R. I
> > thought I'd pass along the fruits of my labor for everyone's amusement.
> >
> > As written, every point is connected to every other point, so feel free
> > to 'start' and 'finish' anywhere you like.
> >
> > Have fun!
> > --Robert
> >
> > PS. Feel free to pass along suggestions or comments.
> >
> >
> You have prb[i] <-p but no definition of i. What was intended?
>
> -pd
> > ----------------------------------------------------------------
> > plotMaze <- function(z, text=FALSE, lwd=2, ...) {
> > N <- nrow(z)
> > y <- -matrix(rep(1:N, N), N, N, byrow=FALSE)-1
> > x <- matrix(rep(1:N, N), N, N, byrow=TRUE)
> > plot(1:(N+1), -1:-(N+1), type="n", ylab="", xlab="", axes=FALSE,
> > ...)
> > segments(1, -1:-(N+1) , N+1, -1:-(N+1), lwd=lwd)
> > segments(1:(N+1), -1, 1:(N+1), -(N+1), lwd=lwd)
> > segments(x+(z==4), y+(z==3), x+(z!=2), y+(z!=1), col="white",
> > lwd=lwd)
> > if (text) text(x+0.5, y+0.5, z)
> > rect(1, -1, N+1, -(N+1), lwd=lwd)
> > }
> >
> >
> > makeMaze <- function(N, p=1) { # large 'p' may result in more order
> > plots
> > z <- matrix(NA+0, N, N)
> > s <- function(x) if (length(x)==1) x else sample(x, size=1)
> > z[s(1:length(z))] <- 0
> > while (any(is.na(z))) {
> > xx <- list(z[c(2:N, N),],
> > z[,c(1, 1:(N-1))],
> > z[c(1, 1:(N-1)),],
> > z[,c(2:N, N)])
> > xx[[1]][N,] <- NA; xx[[2]][,1] <- NA; xx[[3]][1,] <- NA;
> > xx[[4]][,N] <- NA
> > prb <- rep(1, 4); prb[i] <- p
> > for (i in sample(1:4, prob=prb)) {
> > q <- !is.na(xx[[i]]) & is.na(z)
> > if (!any(q)) next
> > z[s(which(q))] <- i
> > break
> > }
> > }
> > z
> > }
> > set.seed(1)
> > plotMaze(makeMaze(10), main="Simple Maze")
> > plotMaze(makeMaze(25), main="Hard Maze", lwd=1)
> >
> >
> > Robert McGehee, CFA
> > Geode Capital Management, LLC
> > One Post Office Square, 28th Floor | Boston, MA | 02109
> > Tel: 617/392-8396 Fax:617/476-6389
> > mailto:robert.mcgehee_at_geodecapital.com
> >
> >
> >
> > This e-mail, and any attachments hereto, are intended fo...{{dropped:11}}
> >
> > ______________________________________________
> > 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.
> >
>
>
> --
> O__ ---- Peter Dalgaard ุster Farimagsgade 5, Entr.B
> c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
> (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard_at_biostat.ku.dk) FAX: (+45) 35327907
>
> ______________________________________________
> R-help_at_r-project.org 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.
>



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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. Received on Tue 29 Apr 2008 - 23:51:09 GMT

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