ggplot2で分割したグラフ毎に異なるtableGrobを書き込む ref: http://qiita.com/nozma/items/a87bbca80b77b3abd161

file0.r

p <- ggplot(mpg, aes(displ, hwy)) +
  geom_point() +
  facet_wrap(~drv) +
  theme_bw() +
  theme(panel.grid = element_blank()) +
  geom_smooth(method = "lm")

file1.r

tpar = list(bg_params = list(fill = "gray", alpha = 0.8)) # 表の外観パラメータ
tg <- mpg %>%
  split(.$drv) %>%
  purrr::map(., ~ (lm(hwy ~ displ, data = .) %>% broom::tidy())[1:2]) %>%
  purrr::map(., ~ data.frame(coef =  round(.[2], 1),
                             row.names = c("(Intercept)", "displ"))) %>%
  purrr::map(., tableGrob,
             theme = ttheme_minimal(
               base_size = 10,
               padding = unit(c(2, 2), "mm"),
               core = tpar,
               colhead = tpar,
               rowhead = tpar
             ))

file2.r

## gtableの作成
g <- ggplot_gtable(ggplot_build(p))

## facetsの取得
facets <- grep("panel", g$layout$name)

## tableGrobを書き込む
g2 <- with(g$layout[facets, ],
           gtable_add_grob(g, tg,
                           t=t, l=l))
plot(g2)