[R] How to make a code last until a condition is completed ?

[William Dunlap]

Look into the while() statement.  E.g.,

f <- function(n, absLimit)
{
    x <- rep(absLimit+1, n) # start with all x,y  outside limits
    y <- x
    while(any(isOutside <- abs(x)>absLimit | abs(y)>absLimit)) {
        x[isOutside] <- rnorm(sum(isOutside), 0, 100)
        y[isOutside] <- rnorm(sum(isOutside), 0, 100)
    }
    list(paths_x=x, paths_y=y)
}
f(n=20, absLimit=100)

Bill Dunlap
TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Gwennaël Bataille
> Sent: Thursday, March 20, 2014 6:47 AM
> To: petr.pikal at precheza.cz
> Cc: r-help at r-project.org
> Subject: Re: [R] How to make a code last until a condition is completed ?
> 
> Dear Petr,
> Thank you for your answer. This will probably save me three lines of
> script, which is appreciable.
> 
> Unfortunately, this does not solve my main issue, that is:
> If my condition is not fulfilled (some points are outside the
> landscape), I have to go back in the script to the first step, again and
> again until the condition "none individual is outside the landscape" is
> fulfilled.
> 
> Is it a trick in R that makes that possible ? Or am I obliged to
> copy-paste : step 1 - step 2 - step 1 -  step 2 .... lot of times and
> hope that the number of steps was sufficient enough to avoid ALL the
> outliers ?
> 
> Regards,
> 
> Gwennaël
> 
> 
> Le 20/03/2014 14:15, PIKAL Petr a écrit :
> > Hi
> >
> > I have a strong suspiction that you want to reinvent wheel.
> >
> > does functions
> > ?chull (grDevices) and ?pip (splancs) do what you want?
> >
> > Regards
> > Petr
> >
> >> -----Original Message-----
> >> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> >> project.org] On Behalf Of Gwennaël Bataille
> >> Sent: Thursday, March 20, 2014 9:55 AM
> >> To: r-help at r-project.org
> >> Subject: [R] How to make a code last until a condition is completed ?
> >>
> >> # Dear all,
> >>
> >> # I simulate individual paths in a landscape (let's say coordinates in
> >> x
> >> and y range
> >> # from -100 to 100 both) and would like to replace each individual
> >> going
> >> outside the
> >> # landscape by a new simulation... until none of them goes outside the
> >> landscape.
> >>
> >> # For example, I simulate 100 coordinates :
> >>
> >> # Step 1 : Simulate the individuals coordinates
> >>
> >> paths_x<- rnorm(100)*100  # This is a simplification for the example
> >> paths_y<- rnorm(100)*100
> >>
> >> # Step 2 : Detect individuals outside the landscape to simulate them
> >> again
> >> # The OUTSIDE variable tells if we need further simulations or not
> >> # The OUTSIDE_IND variable informs about which individuals are outside
> >> the landscape
> >>
> >> IS_OUTSIDE<- c(-min(paths_x), max(paths_x), -min(paths_y),
> >> max(paths_y)) # this gives the absolute value of min and max
> >> if( any(IS_OUTSIDE>  100) ) { OUTSIDE<- TRUE } else { OUTSIDE<- FALSE
> >> }
> >> if(OUTSIDE == TRUE) { OUTSIDE_IND<- c(which(paths_x<  -100),
> >> which(paths_x>  100), which(paths_y<  - 100), which(paths_y>  100)) } #
> >> Identifies the outliers
> >>
> >> # What I would like to do is :
> >>
> >> if( OUTSIDE == TRUE ) {   # Go to step 1 again
> >> paths_x[ OUTSIDE_IND ]<- rnorm(100)[ length( OUTSIDE_IND ) ]*100
> >> paths_y[ OUTSIDE_IND ]<- rnorm(100)[ length( OUTSIDE_IND ) ]*100
> >> }   # And then, go to step 2 again :
> >> # are there some individuals outside the landscape again ? ->  if yes,
> >> go
> >> to step 1 untill none is left
> >>
> >> else { # Go to step 3 }
> >>
> >> # I could easily copy-paste steps 1 and 2 a lot of time, but I want to
> >> make sure all the individuals are OK,
> >> # that none remains outside the landscape "by chance"
> >>
> >> # Thank you very much in advance for your help,
> >>
> >> # Gwennaël Bataille
> >>
> >>
> >> --
> >> Gwennaël BATAILLE, PhD student - Teaching assistant
> >>
> >> Earth and Life Institute
> >> Université Catholique de Louvain
> >> SST/ELI/ELIB
> >> Bâtiment Carnoy, c.145
> >> Croix du sud 4-5, bte L7.07.04
> >> 1348 Louvain-la-Neuve
> >> BELGIUM
> >>
> >> ______________________________________________
> >> 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.
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> 
> --
> Gwennaël BATAILLE, PhD student - Teaching assistant
> 
> Earth and Life Institute
> Université Catholique de Louvain
> SST/ELI/ELIB
> Bâtiment Carnoy, c.145
> Croix du sud 4-5, bte L7.07.04
> 1348 Louvain-la-Neuve
> BELGIUM
> 
> ______________________________________________
> 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.