题
如何将一个人的dput()
S4对象?我想这
require(sp)
require(splancs)
plot(0, 0, xlim = c(-100, 100), ylim = c(-100, 100))
poly.d <- getpoly() #draw a pretty polygon - PRETTY!
poly.d <- rbind(poly.d, poly.d[1,]) # close the polygon because of Polygons() and its kin
poly.d <- SpatialPolygons(list(Polygons(list(Polygon(poly.d)), ID = 1)))
poly.d
dput(poly.d)
请注意,如果我dput()
一个S4对象,我不能再次重建它。你的想法吗?
解决方案
当前标准的,你不能dput
此对象。 dput
的代码包含以下循环:
if (isS4(x)) {
cat("new(\"", class(x), "\"\n", file = file, sep = "")
for (n in slotNames(x)) {
cat(" ,", n, "= ", file = file)
dput(slot(x, n), file = file, control = control)
}
cat(")\n", file = file)
invisible()
}
此手柄S4对象递归的,但它依赖于假定的S3对象将不包含一个S4对象,该对象在你的例子不成立:
> isS4(slot(poly.d,'polygons'))
[1] FALSE
> isS4(slot(poly.d,'polygons')[[1]])
[1] TRUE
的编辑:强>以下是一个变通dput
的局限性。它的工作原理为您提供的例子,但我不认为它会在一般的(例如,它不处理属性)工作。
dput2 <- function (x,
file = "",
control = c("keepNA", "keepInteger", "showAttributes")){
if (is.character(file))
if (nzchar(file)) {
file <- file(file, "wt")
on.exit(close(file))
}
else file <- stdout()
opts <- .deparseOpts(control)
if (isS4(x)) {
cat("new(\"", class(x), "\"\n", file = file, sep = "")
for (n in slotNames(x)) {
cat(" ,", n, "= ", file = file)
dput2(slot(x, n), file = file, control = control)
}
cat(")\n", file = file)
invisible()
} else if(length(grep('@',capture.output(str(x)))) > 0){
if(is.list(x)){
cat("list(\n", file = file, sep = "")
for (i in 1:length(x)) {
if(!is.null(names(x))){
n <- names(x)[i]
if(n != ''){
cat(" ,", n, "= ", file = file)
}
}
dput2(x[[i]], file = file, control = control)
}
cat(")\n", file = file)
invisible()
} else {
stop('S4 objects are only handled if they are contained within an S4 object or a list object')
}
}
else .Internal(dput(x, file, opts))
}
和在这里它是在动作:
> dput2(poly.d,file=(tempFile <- tempfile()))
> poly.d2 <- dget(tempFile)
> all.equal(poly.d,poly.d2)
[1] TRUE
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