shrinkedge: Shrink the edges for the point pattern

In forestSAS: Forest Spatial Structure Analysis Systems

Description

Sometimes, the window of point pattern is too large, we can shrink its edges to the wanted window of point pattern

Usage

shrinkedge(X, xwidth, ywidth, id)

Arguments

X	A point pattern (object of class "ppp").
xwidth	Distance from the edges x coordinates,note xwidth is the half of your width wanted, because the width will shrink both edges in the x coordinates.
ywidth	Distance from the edges y coordinates,note xwidth is the half of your width wanted, because the width will shrink both edges in the y coordinates.
id	Specific identification number of the points in the point pattern.

Details

When expanding for the full pattern, and using expandedge() with a positive xwidth and ywidth; conversely, shrinking for the full pattern, and using shrinkedge () with a negative xwidth and ywidth,the parts of the pattern that are at a distance less than -width from an edge are discarded.

Value

Result returns original data (not a point pattern with the same structure as trees), id is new id of points after edges expanded and old.id is orginal id of points. If xwidth or ywidth = 0, trees are returned unchanged.

Author(s)

Zongzheng Chai, [e-mail]

Examples

library(spatstat)
data(finpines)
finpines$window
# window: rectangle = [-5, 5] x [-8, 2] metres

#Shrink the rectangle [-5,5]x[-8,2] to [-3,3]x[-5,-1]
shrink.trees<- shrinkedge(finpines,xwidth=2,ywidth=3,id=1:126)
shrink.trees

# Show the changes by figures
opar<-par(mfrow=c(1,2))
plot(finpines$x,finpines$y)
text(finpines$x,finpines$y,1:126)
rect(-3,-5,3,-1,border="red")
plot(shrink.trees$x,shrink.trees$y)
text(shrink.trees$x,shrink.trees$y,shrink.trees$old.id)
par(opar)

forestSAS documentation built on May 1, 2019, 10:15 p.m.