tess.R
#
# tess.R
#
# support for tessellations
#
# $Revision: 1.25 $ $Date: 2009/04/05 22:41:32 $
#
tess <- function(..., xgrid=NULL, ygrid=NULL, tiles=NULL, image=NULL,
window=NULL) {
if(!is.null(window))
win <- as.owin(window)
else win <- NULL
isrect <- !is.null(xgrid) && !is.null(ygrid)
istiled <- !is.null(tiles)
isimage <- !is.null(image)
if(isrect + istiled + isimage != 1)
stop("Must specify either (xgrid, ygrid) or tiles or img")
if(isrect) {
stopifnot(is.numeric(xgrid) && all(diff(xgrid) > 0))
stopifnot(is.numeric(ygrid) && all(diff(ygrid) > 0))
if(is.null(win)) win <- owin(range(xgrid), range(ygrid))
ntiles <- (length(xgrid)-1) * (length(ygrid)-1)
out <- list(type="rect", window=win, xgrid=xgrid, ygrid=ygrid, n=ntiles)
} else if(istiled) {
stopifnot(is.list(tiles))
if(!all(unlist(lapply(tiles, is.owin))))
stop("tiles must be a list of owin objects")
if(is.null(win)) {
for(i in seq(along=tiles)) {
if(i == 1)
win <- tiles[[1]]
else
win <- union.owin(win, tiles[[i]])
}
}
win <- rescue.rectangle(win)
out <- list(type="tiled", window=win, tiles=tiles, n=length(tiles))
} else if(isimage) {
image <- eval.im(factor(image))
if(is.null(win)) win <- as.owin(image)
out <- list(type="image", window=win, image=image, n=length(levels(image)))
} else stop("Internal error: unrecognised format")
class(out) <- c("tess", class(out))
return(out)
}
is.tess <- function(x) { inherits(x, "tess") }
print.tess <- function(x, ...) {
cat("Tessellation\n")
win <- x$window
unitinfo <- summary(unitname(win))
switch(x$type,
rect={
equispaced <- function(z) {
dz <- diff(z)
diff(range(dz))/mean(dz) < 0.01
}
if(equispaced(x$xgrid) && equispaced(x$ygrid))
cat(paste("Tiles are equal rectangles, of dimension",
signif(mean(diff(x$xgrid)), 5),
"x",
signif(mean(diff(x$ygrid)), 5),
unitinfo$plural, " ", unitinfo$explain,
"\n"))
else
cat(paste("Tiles are unequal rectangles\n"))
cat(paste(paren(paste(length(x$xgrid)-1, "by",
length(x$ygrid)-1,
"array of tiles")),
"\n"))
},
tiled={
if(win$type == "polygonal")
cat("Tiles are irregular polygons\n")
else
cat("Tiles are windows of general type\n")
cat(paste(length(x$tiles), "tiles\n"))
},
image={
cat(paste("Tessellation is determined by",
"a factor-valued image",
"with", length(levels(x$image)), "levels\n"))
})
print(win)
invisible(NULL)
}
plot.tess <- function(x, ..., main, add=FALSE, col=NULL) {
xname <- deparse(substitute(x))
if(missing(main))
main <- xname
switch(x$type,
rect={
win <- x$window
if(!add)
do.call.matched("plot.owin",
resolve.defaults(list(x=win, main=main),
list(...)),
extrargs=c("sub", "lty", "lwd"))
xg <- x$xgrid
yg <- x$ygrid
do.call.matched("segments",
resolve.defaults(list(x0=xg, y0=win$yrange[1],
x1=xg, y1=win$yrange[2]),
list(col=col),
list(...),
.StripNull=TRUE))
do.call.matched("segments",
resolve.defaults(list(x0=win$xrange[1], y0=yg,
x1=win$xrange[2], y1=yg),
list(col=col),
list(...),
.StripNull=TRUE))
},
tiled={
if(!add)
do.call.matched("plot.owin",
resolve.defaults(list(x=x$window, main=main),
list(...)))
til <- tiles(x)
plotem <- function(z, ..., col=NULL) {
if(is.null(col))
plot(z, ..., add=TRUE)
else if(z$type != "mask")
plot(z, ..., border=col, add=TRUE)
else plot(z, ..., col=col, add=TRUE)
}
lapply(til, plotem, ..., col=col)
},
image={
plot(x$image, main=main, ..., add=add)
})
return(invisible(NULL))
}
"[<-.tess" <- function(x, ..., value) {
switch(x$type,
rect=,
tiled={
til <- tiles(x)
til[...] <- value
ok <- !unlist(lapply(til, is.null))
x <- tess(tiles=til[ok])
},
image={
stop("Cannot assign new values to subsets of a pixel image")
})
return(x)
}
"[.tess" <- function(x, ...) {
switch(x$type,
rect=,
tiled={
til <- tiles(x)[...]
return(tess(tiles=til))
},
image={
img <- x$image
oldlev <- levels(img)
newlev <- unique(oldlev[...])
img <- eval.im(factor(ifelse(img %in% newlev, img, NA)))
levels(img) <- newlev
return(tess(image=img))
})
}
tiles <- function(x) {
switch(x$type,
rect={
out <- list()
xg <- x$xgrid
yg <- x$ygrid
nx <- length(xg) - 1
ny <- length(yg) - 1
for(j in rev(seq(ny)))
for(i in seq(nx)) {
winij <- owin(xg[c(i,i+1)], yg[c(j,j+1)])
dout <- list(winij)
names(dout) <- paste("Tile row ", ny-j+1, ", col ", i,
sep="")
out <- append(out, dout)
}
},
tiled={
out <- x$tiles
if(is.null(names(out)))
names(out) <- paste("Tile", seq(length(out)))
},
image={
out <- list()
ima <- x$image
lev <- levels(ima)
for(i in seq(lev))
out[[i]] <- solutionset(ima == lev[i])
names(out) <- paste(lev)
})
out <- as.listof(out)
return(out)
}
as.im.tess <- function(X,
W=as.mask(as.rectangle(X), dimyx=dimyx), ...,
dimyx=NULL, na.replace=NULL) {
# if W is missing, the default is now evaluated, as above.
# if W is present, it may have to be converted
if(!missing(W)) {
stopifnot(is.owin(W))
if(W$type != "mask")
W <- as.mask(W, dimyx=dimyx)
}
switch(X$type,
tess={
out <- as.im(X$image, W=W, dimyx=dimyx, na.replace=na.replace)
},
tiled={
til <- X$tiles
ntil <- length(til)
xy <- list(x=W$xcol, y=W$yrow)
for(i in seq(ntil)) {
indic <- as.mask(til[[i]], xy=xy)
tag <- as.im(indic, value=i)
if(i == 1) {
out <- tag
outv <- out$v
} else {
outv <- pmin(outv, tag$v, na.rm=TRUE)
}
}
out$v <- outv
out$type <- "factor"
nama <- names(til)
if(is.null(nama) || !all(nzchar(nama)))
nama <- paste(seq(ntil))
levels(out) <- nama
unitname(out) <- unitname(W)
},
rect={
xg <- X$xgrid
yg <- X$ygrid
nrows <- length(yg) - 1
ncols <- length(xg) - 1
out <- as.im(W)
jx <- findInterval(out$xcol, xg, rightmost.closed=TRUE)
iy <- findInterval(out$yrow, yg, rightmost.closed=TRUE)
M <- as.matrix(out)
Jcol <- jx[col(M)]
Irow <- nrows - iy[row(M)] + 1
Ktile <- Jcol + ncols * (Irow - 1)
out <- im(Ktile, xcol=out$xcol, yrow=out$yrow,
lev=seq(nrows * ncols), unitname=unitname(W))
}
)
return(out)
}
as.tess <- function(X) {
UseMethod("as.tess")
}
as.tess.tess <- function(X) {
fields <-
switch(X$type,
rect={ c("xgrid", "ygrid") },
tiled={ "tiles" },
image={ "image" },
stop(paste("Unrecognised tessellation type", sQuote(X$type))))
fields <- c(c("type", "window"), fields)
X <- unclass(X)[fields]
class(X) <- c("tess", class(X))
return(X)
}
as.tess.im <- function(X) {
return(tess(image = X))
}
as.tess.quadratcount <- function(X) {
return(attr(X, "tess"))
}
as.tess.quadrattest <- function(X) {
Y <- attr(X, "quadratcount")
Z <- attr(Y, "tess")
return(Z)
}
as.tess.list <- function(X) {
W <- lapply(X, as.owin)
return(tess(tiles=W))
}
as.tess.owin <- function(X) {
return(tess(tiles=list(X)))
}
intersect.tess <- function(X, Y, ...) {
X <- as.tess(X)
Y <- as.tess(Y)
Xtiles <- tiles(X)
Ytiles <- tiles(Y)
Ztiles <- list()
for(i in seq(Xtiles))
for(j in seq(Ytiles)) {
Tij <- intersect.owin(Xtiles[[i]], Ytiles[[j]], ..., fatal=FALSE)
if(!is.null(Tij))
Ztiles <- append(Ztiles, list(Tij))
}
Xwin <- as.owin(X)
Ywin <- as.owin(Y)
Zwin <- intersect.owin(Xwin, Ywin)
return(tess(tiles=Ztiles, window=Zwin))
}