How to add sparklines in gt package?

Question

I want to create a table which show how data changed in past months. I've been trying to do it in gt package I couldn't understand why it doesn't work.

example data

df <- data.frame(
  group = c("x", "x", "y", "y", "z", "z"),
  sub_group = c("1", "2", "1", "2", "1", "2"),
  jan = c(1, 2, 3, 3, 4, 1),
  feb = c(2, 3, 1, 3, 2, 4),
  mar = c(9, 2, 5, 3, 1, 4)
)

I've tried gt_plt_sparkline function two different ways.

1. First I added a column like it said in the wiki.

data %>%
  mutate(summary = list(data[1,3:5])) %>%
  gt() %>% 
  gt_plt_sparkline(column = 6)

this resulted where every sparkline is sparkline of first group

2. I've tried to manipulate it with row function

data %>%
  mutate(summary = list(data[row(data),3:5])) %>%
  gt() %>% 
  gt_plt_sparkline(column = 6)

but this throw the error Error in FUN(X[[i]], ...) : 'list' object cannot be coerced to type 'double'

Is there a way around this or should I change data structure?

Answer 1

Here is one option to create the desired list column for each sparkline using purrr::map_dbl:

library(gt)
library(gtExtras)
library(dplyr, warn = FALSE)
library(purrr)

df |>
  group_by(group, sub_group) |>
  mutate(
    col_spark = list(
      purrr::map_dbl(
        pick(everything()), \(x) matrix(x)[1, , drop = TRUE]
      )
    )
  ) %>%
  ungroup() |>
  gt() %>%
  gt_plt_sparkline(column = 6)