spatstat (version 1.31-3)

transect.im: Pixel Values Along a Transect

Description

Extract the pixel values of a pixel image at each point along a linear transect.

Usage

transect.im(X, ..., from="bottomleft", to="topright",
             click=FALSE, add=FALSE)

Arguments

X

A pixel image (object of class "im").

...

Ignored.

from,to

Optional. Start point and end point of the transect. Pairs of $(x,y)$ coordinates in a format acceptable to xy.coords, or keywords "bottom", "left", "top"

click

Optional. Logical value. If TRUE, the linear transect is determined interactively by the user, who clicks two points on the current plot.

add

Logical. If click=TRUE, this argument determines whether to perform interactive tasks on the current plot (add=TRUE) or to start by plotting X (add=FALSE).

Value

• An object of class "fv" which can be plotted.

Details

The pixel values of the image X along a line segment will be extracted. The result is a function table ("fv" object) which can be plotted directly.

If click=TRUE, then the user is prompted to click two points on the plot of X. These endpoints define the transect.

Otherwise, the transect is defined by the endpoints from and to. The default is a diagonal transect from bottom left to top right of the frame.

See Also

im

Examples

Z <- density(redwood)
  plot(transect.im(Z))
  plot(transect.im(Z, click=TRUE))