integral.im

0th

Percentile

Integral of a Pixel Image

Computes the integral of a pixel image.

Keywords
spatial, math
Usage
integral(f, domain=NULL, ...)

## S3 method for class 'im': integral(f, domain=NULL, \dots)

Arguments
f
A pixel image (object of class "im") with pixel values that can be treated as numeric or complex values.
domain
Optional. Window specifying the domain of integration.
...
Ignored.
Details

The function integral is generic, with methods for "im", "msr", "linim" and "linfun". The method integral.im treats the pixel image f as a function of the spatial coordinates, and computes its integral. The integral is calculated by summing the pixel values and multiplying by the area of one pixel.

The pixel values of f may be numeric, integer, logical or complex. They cannot be factor or character values.

The logical values TRUE and FALSE are converted to 1 and 0 respectively, so that the integral of a logical image is the total area of the TRUE pixels, in the same units as unitname(x).

Value

  • A single numeric or complex value.

See Also

eval.im, [.im

Aliases
  • integral
  • integral.im
Examples
# approximate integral of f(x,y) dx dy
   f <- function(x,y){3*x^2 + 2*y}
   Z <- as.im(f, square(1))
   integral.im(Z)
   # correct answer is 2

   D <- density(cells)
   integral.im(D)
   # should be approximately equal to number of points = 42

   # integrate over the subset [0.1,0.9] x [0.2,0.8]
   W <- owin(c(0.1,0.9), c(0.2,0.8))
   integral.im(D, W)
Documentation reproduced from package spatstat, version 1.41-1, License: GPL (>= 2)

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