[R] intervals from cut() as numerics?

[Dimitrios Rizopoulos]

as an alternative, you can have a look inside cut.default and use the 
part that produces the breaks, i.e.,

breaks <- 10
groups <- cut(x, breaks = breaks)
max.bias <- as.vector(tapply(error, groups, mean))

# from cut.default()
nb <- as.integer(breaks + 1)
dx <- diff(rx <- range(x, na.rm = TRUE))
breaks <- round(seq(rx[1] - dx/1000, rx[2] + dx/1000, len = nb), 2)
mat <- cbind(breaks[1:(nb - 1)], breaks[2:nb])

plot(x, error, type = "n")
abline(h = 0, col = "grey")
panel.smooth(x, error)
arrows(mat[, 1], max.bias, mat[, 2], max.bias, length = 0.05, 
angle = 90, code = 3)


Best,
Dimitris

---- 
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


Quoting Gavin Simpson <gavin.simpson at ucl.ac.uk>:

> On Sat, 2006-05-20 at 17:39 +0800, Berwin A Turlach wrote:
> > G'day Gavin,
> > 
> > >>>>> "GS" == Gavin Simpson <gavin.simpson at ucl.ac.uk> writes:
> > 
> >     GS> The problem is getting the range/interval for each group
> from
> >     GS> (4,4.3], so I can automate this.
> > Most likely there is an easier way, but this seems to work:
> > 
> > ## get the levels of groups:
> > > tmp <- levels(groups)
> > ## remove the opening "(" and closing "]" from the string:
> > > tmp1 <- sapply(tmp, function(x) substr(x, 2, nchar(x)-1))
> > ## split into two character strings:
> > > tmp2 <- strsplit(tmp1, ",")
> > ## turn into results into two numbers:
> > > tmp3 <- lapply(tmp2, as.numeric)
> > 
> > ## Of course, we can do everything in one go:
> > > lapply(strsplit(sapply(levels(groups), function(x) substr(x, 2,
> nchar(x)-1)), ","), as.numeric)
> 
> Many thanks Berwin. My brain wasn't in character string processing
> mode,
> but your solution works just fine. For the archives then, here is
> the
> full script:
> 
> ## example data
> dat <- seq(4, 7, by = 0.05)
> x <- sample(dat, 30) 
> y <- sample(dat, 30)
> ## residuals
> error <- x - y
> ## break range of x into 10 groups
> groups <- cut(x, breaks = 10)
> ##calculate bias (mean) per group
> max.bias <- aggregate(error, list(group = groups), mean)$x
> ## turn cut intervals into numeric
> interv <- lapply(strsplit(sapply(levels(groups), 
>                                  function(x) substr(x, 2, 
>                                                     nchar(x)-1)),
> ","),
>                  as.numeric)
> ## reformat cut intervals as 2 col matrix for easy plotting
> interv <- matrix(unlist(interv), ncol = 2, byrow = TRUE)
> ## plot the residuals vs observed
> plot(x, error, type = "n")
> abline(h = 0, col = "grey")
> panel.smooth(x, error)
> ## add bias indicators per group
> arrows(interv[,1], max.bias, interv[,2], max.bias, 
>        length = 0.05, angle = 90, code = 3)
> 
> All the best,
> 
> G
> 
> <snip />
> > Cheers,
> > 
> >         Berwin
> > 
> > ========================== Full address
> ============================
> > Berwin A Turlach                      Tel.: +61 (8) 6488 3338
> (secr)   
> > School of Mathematics and Statistics        +61 (8) 6488 3383
> (self)      
> > The University of Western Australia   FAX : +61 (8) 6488 1028
> > 35 Stirling Highway                   
> > Crawley WA 6009                e-mail: berwin at maths.uwa.edu.au
> > Australia                       
> http://www.maths.uwa.edu.au/~berwin
> > 
> -- 
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
~%
>  *Note new Address and Fax and Telephone numbers from 10th April
> 2006*
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
~%
> Gavin Simpson                     [t] +44 (0)20 7679 0522
> ECRC                              [f] +44 (0)20 7679 0565
> UCL Department of Geography
> Pearson Building                  [e] gavin.simpsonATNOSPAMucl.ac.uk
> Gower Street
> London, UK                        [w]
> http://www.ucl.ac.uk/~ucfagls/cv/
> WC1E 6BT                          [w] http://www.ucl.ac.uk/~ucfagls/
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
~%
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
> 
> 


Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm