在 Rscript 中使用 grid.edit() 的问题

Question

我在使用来自Rscript 的grid.edit() 时遇到问题。我正在使用grid.edit() 来增加图例和图表中空心点的厚度。我从这篇文章 (Change thickness of a marker in ggplot2) 中获取了这个。只是看起来更好海事组织。我知道从源文件和 Rscripts 中，您可以使用 print(p) 获取要绘制的 ggplot 对象，但我需要使用 grid.edit()，所以我不知道如何解决这个问题。下面的工作示例。

我的 R 脚本名为 test.r

library(ggplot2)
library(grid)
library(gtable)

p <- ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(shape = factor(cyl))) + scale_shape(solid = FALSE)
lwd = 2   # Set line width
g = ggplotGrob(p); dev.off()  # Get the plot grob
# Get the indices for the legend: t = top, r = right, ...
indices <- c(subset(g$layout, name == "guide-box", select = t:r))
# Get the row number of the legend in the layout
rn <- which(g$layout$name == "guide-box")
# Extract the legend
legend <- g$grobs[[rn]]
# Get the legend keys
pointGrobs = which(grepl("points", legend$grobs[[1]]$grobs))
# Check them out - no line width set
# for (i in pointGrobs) str(legend$grobs[[1]]$grobs[[i]])
# Set line width
for (n in pointGrobs) legend$grobs[[1]]$grobs[[n]]$gp$lwd = lwd
# Check them out - line width set
# for (i in pointGrobs) str(legend$grobs[[1]]$grobs[[i]])
# Put the modified legend back into the plot grob
g$layout$clip[g$layout$name == "panel"] <- "off"
g = gtable_add_grob(g, legend, t=indices$t, l=indices$l)
###g$grobs[[4]]$children[[2]]$gp$lwd = gpar(lwd = lwd)  # Alternative for setting lwd for points in the plot
grid.newpage()
grid.draw(g)
grid.edit("geom_point.points", grep = TRUE, gp = gpar(lwd = lwd))

dev.print(cairo_pdf,filename="Aplot.pdf",
 width=11, 
height=8.5)

我的批处理文件。

...\R-3.2.3\bin\x64\Rscript.exe test.r
PAUSE

脚本运行，但出现以下错误。

Error in editDLfromGPath(gPath,specs,strict,grep,global,redraw):
    'gPath' (geom_point.points) not found
Calls: grid.edit -> editDLfromGPath
Execution halted

另外一个 PDF 被打印到我的名为 Rplots 的工作目录中。该图是默认大小，有趣的是图例中的点很粗，但图中的点不是。似乎脚本在grid.edit() 处失败，但grid.draw() 成功。

Answer 1

您需要grid.force() 绘图，以便网格编辑功能可以看到所有的 grobs。我已经增加了点的大小和线宽倍数，这样编辑就很明显已经生效了。

library(ggplot2)
library(grid)
library(gtable)

p <- ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(shape = factor(cyl)), size = 5) + scale_shape(solid = FALSE)
lwd = 3   # Set line width
g = ggplotGrob(p); dev.off()  # Get the plot grob
# Get the indices for the legend: t = top, r = right, ...
indices <- c(subset(g$layout, name == "guide-box", select = t:r))
# Get the row number of the legend in the layout
rn <- which(g$layout$name == "guide-box")
# Extract the legend
legend <- g$grobs[[rn]]
# Get the legend keys
pointGrobs = which(grepl("points", legend$grobs[[1]]$grobs))
# Check them out - no line width set
# for (i in pointGrobs) str(legend$grobs[[1]]$grobs[[i]])
# Set line width
for (n in pointGrobs) legend$grobs[[1]]$grobs[[n]]$gp$lwd = lwd
# Check them out - line width set
# for (i in pointGrobs) str(legend$grobs[[1]]$grobs[[i]])
# Put the modified legend back into the plot grob
g$layout$clip[g$layout$name == "panel"] <- "off"
g = gtable_add_grob(g, legend, t=indices$t, l=indices$l)
###g$grobs[[4]]$children[[2]]$gp$lwd = gpar(lwd = lwd)  # Alternative for setting lwd for points in the plot
grid.newpage()
grid.draw(g)

grid.ls()
grid.ls(grid.force())  # Note the difference here

grid.force()
grid.edit("geom_point.points", grep = TRUE, gp = gpar(lwd = lwd))


# Or to edit the grob (rather than edit on screen)
g = editGrob(grid.force(g), "geom_point.points", grep = TRUE, gp = gpar(lwd = lwd))
grid.newpage()
grid.draw(g)

# To give it a print method
print.ggplotgrob <- function(x) {
   grid.newpage()   
   grid.draw(x)
}
class(g) = c("ggplotgrob", class(g)) 

g

我的 sessionInfo()

R version 3.2.3 (2015-12-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=English_Australia.1252  LC_CTYPE=English_Australia.1252   
[3] LC_MONETARY=English_Australia.1252 LC_NUMERIC=C                      
[5] LC_TIME=English_Australia.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] Cairo_1.5-9   gtable_0.2.0  ggplot2_2.1.0

loaded via a namespace (and not attached):
[1] labeling_0.3     colorspace_1.2-6 scales_0.4.0     plyr_1.8.3      
[5] tools_3.2.3      Rcpp_0.12.3      digest_0.6.9     munsell_0.4.3