莱迪思的`panel.rug`产生不同的线长和宽图

Question

当使用包含panel.rug()的边距在格子中生成宽图时，粗糙边距中的线条长度在y轴上比x轴更长：

library(lattice)
png(width=800, height=400)
xyplot(Fertility ~ Education, swiss, panel = function(x, y,...) {
  panel.xyplot(x, y, col=1, pch=16)
  panel.rug(x, y, col=1, end= ...)})
dev.off()

我希望x轴和y轴上的 rug 线条长度相同，而不管图形的形状如何（注意：现在 rug 线条当情节是正方形时，只会是相同的长度。

Answer 1

使用点阵，只需将panel.rug使用的坐标系从默认值"npc"更改为"snpc"：

library(lattice)

## png(width=800, height=400)
xyplot(Fertility ~ Education, swiss, panel = function(x, y,...) {
  panel.xyplot(x, y, col=1, pch=16)
  panel.rug(x = x, y = y,  
            x.units = rep("snpc", 2),  y.units = rep("snpc", 2), 
            col=1, end= ...)
})
## dev.off()

要查看为什么这可以获得您想要的内容，请参阅?unit，了解这两个坐标系的含义：

 Possible ‘units’ (coordinate systems) are:

 ‘"npc"’ Normalised Parent Coordinates (the default).  The origin
      of the viewport is (0, 0) and the viewport has a width and
      height of 1 unit.  For example, (0.5, 0.5) is the centre of
      the viewport.

 ‘"snpc"’ Square Normalised Parent Coordinates.  Same as Normalised
      Parent Coordinates, except gives the same answer for
      horizontal and vertical locations/dimensions.  It uses the
      _lesser_ of npc-width and npc-height.  This is useful for
      making things which are a proportion of the viewport, but
      have to be square (or have a fixed aspect ratio).