R - 无法访问插槽？

Question

当我尝试将 georeferenced tif-files 添加到我在 R 中的 ggplots 中时，我遇到了一个看似奇怪的 槽问题：使用 @ 加载光栅文件后987654322@我无法到达它的colortable-slot：

>>Grab the example tif-file<<:

raster1 <- raster(paste(workingDir, "/HUEK200_Durchlaessigkeit001_proj001.tif", sep="", collapse=""))
raster1@colortable  #or
slot(raster1, "colortable")

最后两行应该同样工作，但都会导致错误消息：

Error in slot(raster1, "colortable") : 
  no slot of name "colortable" for this object of class "RasterLayer"

这令人困惑，因为通过attributes(raster1) 对属性的一瞥清楚地列出了该插槽：

Slot "colortable":
  [1] "#FFFFFF" "#000000" "#B49ED7" "#9B7DCF" "#9EAAD7" "#B2BEEB" "#B4EBB4"
  [8] "#F5E1B5" "#CCB792" "#B9A08C" "#0070FF" "#0000C8" "#F8F8F8" "#DBF5FF"
 [15] "#B14D00" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [22] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [29] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [36] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [43] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [50] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [57] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [64] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [71] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [78] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [85] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [92] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
 [99] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[106] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[113] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[120] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[127] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[134] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[141] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[148] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[155] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[162] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[169] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[176] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[183] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[190] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[197] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[204] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[211] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[218] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[225] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[232] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[239] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[246] "#000000" "#000000" "#000000" "#000000" "#000000" "#000000" "#000000"
[253] "#000000" "#000000" "#000000" "#000000"

首先是我做错了什么还是可能是一个错误？我怎样才能最终访问颜色表？我通过调用plot(raster1) 知道它应该可以工作，因为该图显示了正确的颜色集。此外：通常，在管理空间多边形对象时，S4object@someslot-方法对我来说效果很好。

编辑： 在colortable 旁边尝试访问attributes(raster1) 的其他插槽列表时会出现相同的错误。

感谢您的帮助！

Answer 1

我现在自己找到了答案。我只是误读了attributes(raster1) 的（不完全明显的）输出。 colortable-slot 不是直接（一阶）光栅对象接口的一部分，如果你可以在 R 中这样称呼它的话。而是在legend 中列出，如下所示：

attr(raster1, "legend")@colortable

R 中的引用总是让我感到惊讶！ :)