如何在tableGrob的底部添加一行？

Question

说我有这样一张桌子：

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

我把它变成了一个像这样的tableGrob：

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（改变t = 1到t = 2，b = 1到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()

有任何想法吗？为什么特意尝试在底部添加一行失败？

Answer 1

表

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

分配给变量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)