shrinkedge {forestSAS} | R Documentation |
Shrink the edges for the point pattern
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, chaizz@126.com
Examples
library(spatstat.data)
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)