如何在 tableGrob 的底部添加一行？

Question

假设我有一个 table 这样的：

df1 <- data.frame(x=1,y=1,z=1)

我把它变成了 table像这样的 Grob：

tableGrob(df1,rows = NULL) %>% grid.draw()

如何在底部添加一行？

我可以像这样在顶部添加一行：

tableGrob(df1,rows = NULL) %>%   gtable_add_grob(
grobs = segmentsGrob( # line across the bottom
  x0 = unit(0,"npc"),
  y0 = unit(1,"npc"),
  x1 = unit(2,"npc"),
  y1 = unit(1,"npc"),
  gp = gpar(lwd = 2)),
t = 1, b = 1, l = 1, r = 3) %>% grid.draw()

或者像这样的第二行（将 t=1 更改为 t=2 并将 b=1 更改为 b=2）：

tableGrob(df1,rows = NULL) %>%   gtable_add_grob(
grobs = segmentsGrob( # line across the bottom
  x0 = unit(0,"npc"),
  y0 = unit(1,"npc"),
  x1 = unit(2,"npc"),
  y1 = unit(1,"npc"),
  gp = gpar(lwd = 2)),
t = 2, b = 2, l = 1, r = 3) %>% grid.draw()

但是当我尝试这个时（t=3 和 b=3）：

tableGrob(df1,rows = NULL) %>%   gtable_add_grob(
grobs = segmentsGrob( # line across the bottom
  x0 = unit(0,"npc"),
  y0 = unit(1,"npc"),
  x1 = unit(2,"npc"),
  y1 = unit(1,"npc"),
  gp = gpar(lwd = 2)),
t = 3, b = 3, l = 1, r = 3) %>% grid.draw()

我收到以下错误：

Error in grid.Call.graphics(C_setviewport, vp, TRUE) :   invalid 'layout.pos.row'

此外，这不起作用（t=2 和 b=2，但 y0=2 和 y1=2）：

tableGrob(df1,rows = NULL) %>%   gtable_add_grob(
grobs = segmentsGrob( # line across the bottom
  x0 = unit(0,"npc"),
  y0 = unit(2,"npc"),
  x1 = unit(2,"npc"),
  y1 = unit(2,"npc"),
  gp = gpar(lwd = 2)),
t = 2, b = 2, l = 1, r = 3) %>% grid.draw()

有什么想法吗？为什么在底部添加一行的尝试特别失败？

Answer 1

Table

df1 <- data.frame(x=1,y=1,z=1)

赋值给变量g1

g1 <- tableGrob(df1,rows = NULL)


g1 <- gtable_add_grob(g1,
                     grobs = segmentsGrob( # line across the bottom
                       x0 = unit(0,"npc"),
                       y0 = unit(0,"npc"),
                       x1 = unit(1,"npc"),
                       y1 = unit(0,"npc"),
                       gp = gpar(lwd = 2.0)),
                     t = 2, b = 2, l = 1, r = ncol(g1))
grid.draw(g1)

如何在 tableGrob 的底部添加一行？

How do i add a line to the bottom of a tableGrob?

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