在水平图面板区域之外添加文本 [英] Add text out of levelplot panel area

问题描述

我想在levelplot的绘图区域之外添加文本.在下面的示例中，我需要在指定位置的某个地方输入文本.

I want to add text out of plot area in levelplot. In the following example, I need the text in somewhere in the pointed location.

library (raster)
library(rasterVis)

f <- system.file("external/test.grd", package="raster")
r <- raster(f)
levelplot(r) 

我尝试了多行文字功能，但没有成功.有什么建议吗?

I tried mtext function with no success. Any suggestions?

mtext("text", side=3, line=0)

推荐答案

tldr;

您可以使用较低级别的网格图形功能对图进行注释.在这种情况下，请执行以下操作:

tldr;

You can annotate the plot using lower-level grid graphical functions. In this case, do something like:

library(grid)
seekViewport("plot_01.legend.top.vp")
grid.text("Hello", x=0, y=unit(1,"npc") + unit(0.4, "lines"), just=c("left", "bottom"),
          gp=gpar(cex=1.6))

---

rasterVis 和其他基于 lattice 的程序包使用 grid 图形系统，而不是mtext()组成部分的基本图形系统

---

rasterVis and other lattice-based packages use the grid graphical system, not the base graphical system of which mtext() is a part.

在这里，我将使用 grid 来在视口左上角上方0.4行的位置添加文本(技术性 grid 术语) )，并在其中打印上边距图.

Here, using grid, is how I'd go about adding text at a position 0.4 lines above the upper-left corner of the viewport (a technical grid term) in which that upper margin plot is printed.

• 首先，找到相关视口的名称.

• First, find the name of the relevant viewport.

library(grid)
levelplot(r)
grid.ls(viewport=TRUE, grobs=FALSE)  ## Prints out a listing of all viewports in plot

快速浏览grid.ls()返回的列表，会显示一个名为plot_01.legend.top.vp的视口，看起来像是一个有前途的候选对象.如果要检查它是否正确，可以在其周围绘制一个矩形，如下所示(使用视口的完整路径):

A quick scan of the listing returned by grid.ls() turns up a viewport named plot_01.legend.top.vp, which looks like a promising candidate. If you'd like to check whether it's the correct one, you can plot a rectangle around it with something like the following (which uses the full path to the viewport):

grid.rect(vp = "plot_01.toplevel.vp::plot_01.legend.top.vp",
          gp = gpar(col = "red"))

然后，使用 grid 的灵活的坐标系，将所需的文本放置在该视口的左上角上方.

Then, using grid's terrifically flexible coordinate system, place the desired text just above the upper left corner of that viewport.

ll <- seekViewport("plot_01.legend.top.vp")
grid.text("Hello", x = 0, y = unit(1,"npc") + unit(0.4, "lines"), 
          just = c("left", "bottom"),
          gp = gpar(cex=1.6))
upViewport(ll)  ## steps back up to viewport from which seekViewport was called

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