R: Histogram of Pixel Values in an Image

hist.im {spatstat} | R Documentation

## Histogram of Pixel Values in an Image

### Description

Computes and displays a histogram of the pixel values in a pixel image. The `hist` method for class `"im"`.

### Usage

      ## S3 method for class 'im'
    hist(x, ..., probability=FALSE, xname)

### Arguments

`x` | A pixel image (object of class `"im"`).
`...` | Arguments passed to `hist.default` or `barplot`.
`probability` | Logical. If `TRUE`, the histogram will be normalised to give probabilities or probability densities.
`xname` | Optional. Character string to be used as the name of the dataset `x`.

### Details

This function computes and (by default) displays a histogram of the pixel values in the image `x`.

An object of class `"im"` describes a pixel image. See `im.object`) for details of this class.

The function `hist.im` is a method for the generic function `hist` for the class `"im"`.

Any arguments in `...` are passed to `hist.default` (for numeric valued images) or `barplot` (for factor or logical images). For example, such arguments control the axes, and may be used to suppress the plotting.

### Value

For numeric-valued images, an object of class `"histogram"` as returned by `hist.default`. This object can be plotted.

For factor-valued or logical images, an object of class `"barplotdata"`, which can be plotted. This is a list with components called `counts` (contingency table of counts of the numbers of pixels taking each possible value), `probs` (corresponding relative frequencies) and `mids` (graphical x-coordinates of the midpoints of the bars in the barplot).

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz

### See Also

`spatialcdf` for the cumulative distribution function of an image.

`hist`, `hist.default`, `barplot`.

For other statistical graphics such as Q-Q plots, use `X[]` to extract the pixel values of image `X`, and apply the usual statistical graphics commands.

For information about pixel images see `im.object`, `summary.im`.

### Examples

      X <- as.im(function(x,y) {x^2}, unit.square())
      hist(X)
      hist(cut(X,3))

[Package spatstat version 1.63-3 Index]