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emptyspace.R
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79 lines (79 loc) · 1.68 KB
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emptyspace<-function(x,y=NULL) {
xlim<-par("usr")[1:2]
ylim<-par("usr")[3:4]
if(is.null(y)) {
if(is.list(x)) {
# trust me, I'm a list
y<-as.vector(x[[2]])
x<-as.vector(x[[1]])
}
else stop("both x and y values must be supplied")
}
xyna<-which(is.na(x) | is.na(y))
if(any(xyna)) {
# get rid of any NAs
x<-x[-xyna]
y<-y[-xyna]
}
# check for negative values and offset them out
xoffset<-yoffset<-0
if(any(x < 0)) {
xoffset<-min(x)
x<-x-xoffset
xlim<-xlim-xoffset
}
if(any(y < 0)) {
yoffset<-min(y)
y<-y-yoffset
ylim<-ylim-yoffset
}
# here begins Ray Brownrigg's code
ox<-order(x)
x<-x[ox]
y<-y[ox]
x<-c(xlim[1],x,xlim[2])
y<-c(ylim[1],y,ylim[2])
omaxa<-0
halfxspan<-diff(xlim)/2
halfyspan<-diff(ylim)/2
# added braces here for clarity
for(i in 1:(length(x)-1)) {
for(j in (i+1):length(x)) {
x1<-x[i]
x2<-x[j]
XX<-x2 - x1
# if(XX > halfxspan) break
yy<-c(ylim[1],y[(i+1):(j-1)],ylim[2])
oyy<-order(yy)
yy<-yy[oyy]
dyy<-diff(yy)
# whichdyy<-(dyy <= halfyspan) & (dyy >= 0.5*XX) & (dyy <= 2*XX)
# the next line fixes the problem with very large empty spaces
whichdyy<-(dyy >= 0.5*XX) & (dyy <= 2*XX)
wy1<-yy[whichdyy]
if(length(wy1) > 0) {
wy2<-yy[(1:length(dyy))[whichdyy]+1]
k<-which.max(dyy[whichdyy])
maxa<-(x2-x1)*(wy2[k]-wy1[k])
if(maxa > omaxa) {
omaxa<-maxa
mx1<-x1
mx2<-x2
my1<-wy1[k]
my2<-wy2[k]
}
}
}
}
# if offsets were used, remove them from the final values
if(xoffset < 0) {
mx1<-mx1+xoffset
mx2<-mx2+xoffset
}
if(yoffset < 0) {
my1<-my1+yoffset
my2<-my2+yoffset
}
# return the center of the rectangle
return(list(x=(mx1+mx2)/2,y=(my1+my2)/2))
}