R: Convert Line Segment Pattern to Pixel Image

pixellate.psp {spatstat.geom} | R Documentation

## Convert Line Segment Pattern to Pixel Image

### Description

Converts a line segment pattern to a pixel image by measuring the length or number of lines intersecting each pixel.

### Usage

    ## S3 method for class 'psp'
    pixellate(x, W=NULL, ..., weights = NULL,
                            what=c("length", "number"),
                            DivideByPixelArea=FALSE)

### Arguments

`x` | Line segment pattern (object of class `"psp"`).
`W` | Optional window (object of class `"owin"`) determining the pixel resolution.
`...` | Optional arguments passed to `as.mask` to determine the pixel resolution.
`weights` | Optional vector of weights associated with each line segment.
`what` | String (partially matched) indicating whether to compute the total length of intersection (`what="length"`, the default) or the total number of segments intersecting each pixel (`what="number"`).
`DivideByPixelArea` | Logical value, indicating whether the resulting pixel values should be divided by the pixel area.

### Details

This function converts a line segment pattern to a pixel image by computing, for each pixel, the total length of intersection between the pixel and the line segments. Alternatively it can count the number of line segments intersecting each pixel.

This is a method for the generic function `pixellate` for the class of line segment patterns.

The pixel raster is determined by `W` and the optional arguments `...`. If `W` is missing or `NULL`, it defaults to the window containing `x`. Then `W` is converted to a binary pixel mask using `as.mask`. The arguments `...` are passed to `as.mask` to control the pixel resolution.

If `weights` are given, then the length of the intersection between line segment `i` and pixel `j` is multiplied by `weights[i]` before the lengths are summed for each pixel.

### Value

A pixel image (object of class `"im"`) with numeric values.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### See Also

`pixellate`, `as.mask`, `as.mask.psp`.

Use `as.mask.psp` if you only want to know which pixels are intersected by lines.

### Examples

      X <- psp(runif(10),runif(10), runif(10), runif(10), window=owin())
      plot(pixellate(X))
      plot(X, add=TRUE)
      sum(lengths_psp(X))
      sum(pixellate(X))
      plot(pixellate(X, what="n"))

[Package spatstat.geom version 2.3-2 Index]