R: Compute the Number of Classes for a Histogram

nclass {grDevices} | R Documentation

## Compute the Number of Classes for a Histogram

### Description

Compute the number of classes for a histogram.

### Usage

    nclass.Sturges(x)
    nclass.scott(x)
    nclass.FD(x)

### Arguments

`x` | A data vector.

### Details

`nclass.Sturges` uses Sturges' formula, implicitly basing bin sizes on the range of the data.

`nclass.scott` uses Scott's choice for a normal distribution based on the estimate of the standard error, unless that is zero where it returns `1`.

`nclass.FD` uses the Freedman-Diaconis choice based on the inter-quartile range (`IQR`) unless that's zero where it reverts to `mad(x, constant=2)` and when that is 0 as well, returns `1`.

### Value

The suggested number of classes.

### References

Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S-PLUS. Springer, page 112.

Freedman, D. and Diaconis, P. (1981) On the histogram as a density estimator: L_2 theory. Zeitschrift für Wahrscheinlichkeitstheorie und verwandte Gebiete 57, 453–476.

Scott, D. W. (1979) On optimal and data-based histograms. Biometrika 66, 605–610.

Scott, D. W. (1992) Multivariate Density Estimation. Theory, Practice, and Visualization. Wiley.

Sturges, H. A. (1926) The choice of a class interval. Journal of the American Statistical Association 21, 65–66.

### See Also

`hist` and `truehist` (package MASS); `dpih` (package KernSmooth) for a plugin bandwidth proposed by Wand(1995).

### Examples

    set.seed(1)
    x <- stats::rnorm(1111)
    nclass.Sturges(x)

    ## Compare them:
    NC <- function(x) c(Sturges = nclass.Sturges(x),
          Scott = nclass.scott(x), FD = nclass.FD(x))
    NC(x)
    onePt <- rep(1, 11)
    NC(onePt) # no longer gives NaN

[Package grDevices version 2.15.1 Index]