Class breaks

Finds class breaks in a distribution

classBreaks(x, n, type = c("equal", "quantile", "std", "geometric"))

Arguments

x	A vector to find breaks for
n	Number of breaks
type	Statistic used to find breaks c("equal", "quantile", "std", "geometric")

Value

A vector containing class break values the length is n+1 to allow for specification of ranges

Note

The robust std method uses sqrt(sum(x^2)/(n-1)) to center the data before deriving "pretty" breaks.

Author

Jeffrey S. Evans <jeffrey_evans@tnc.org>

Examples

 y <- rnbinom(100, 10, 0.5)
   classBreaks(y, 10)  
#>  [1]  1.0  3.1  5.2  7.3  9.4 11.5 13.6 15.7 17.8 19.9 22.0
   classBreaks(y, 10, type="quantile")
#>   0%  10%  20%  30%  40%  50%  60%  70%  80%  90% 100% 
#>    1    5    6    7    8    9   10   10   13   15   22 
 
opar <- par(no.readonly=TRUE)
   par(mfrow=c(2,2))
     d <- density(y)
     plot(d, type="n", main="Equal Area breaks")
       polygon(d, col="cyan")
       abline(v=classBreaks(y, 10)) 
     plot(d, type="n", main="Quantile breaks")
       polygon(d, col="cyan")
       abline(v=classBreaks(y, 10, type="quantile"))
     plot(d, type="n", main="Robust Standard Deviation breaks")
       polygon(d, col="cyan")
       abline(v=classBreaks(y, 10, type="std"))
     plot(d, type="n", main="Geometric interval breaks")
       polygon(d, col="cyan")
       abline(v=classBreaks(y, 10, type="geometric"))
 par(opar)
  
 ( y.breaks <- classBreaks(y, 10) )     
#>  [1]  1.0  3.1  5.2  7.3  9.4 11.5 13.6 15.7 17.8 19.9 22.0
 cut(y, y.breaks, include.lowest = TRUE, labels = 1:10)
#>   [1] 4  3  2  6  3  3  4  5  3  4  6  4  3  4  7  2  3  7  4  1  7  2  6  4  7 
#>  [26] 3  4  1  4  2  4  1  4  7  5  2  6  4  4  6  7  9  2  3  8  5  3  3  2  7 
#>  [51] 3  6  5  5  6  8  9  2  2  4  3  2  5  1  8  4  2  4  3  3  5  5  3  10 8 
#>  [76] 5  5  3  4  3  4  5  5  1  5  3  6  1  3  5  7  5  4  4  4  5  4  6  8  3 
#> Levels: 1 2 3 4 5 6 7 8 9 10