Why am I getting invalid values when using flextable's tabulator() function?

I am new to R and using its library. I am trying to make a table where the headers are in the values of the columns itself and am using flextable.

Here is my goal (mock-up) where there are multiple header levels:

Here is the documentation on flextable's tabulator: https://ardata-fr.github.io/flextable-book/tabulation.html

Here is my attempt (example data):

library(flextable)
library(dplyr)

df <- data.frame(question = c("Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction"),
                 column_one = c("Portion Size", "Portion Size", "Portion Size", "Portion Size", "Portion Size", "Portion Size", "Region", "Region", "Region", "Region"),
                 column_two = c("Small", "Medium", "Large", "Small", "Medium", "Large", "West", "East", "West", "East"),
                 row = c("Pizza", "Pizza", "Pizza", "Hamburger", "Hamburger", "Hamburger", "Pizza", "Pizza", "Hamburger", "Hamburger"),
                 percent = c(0.83679353, 0.341159874, 0.084278807, 0.071733007, 0.363397833, 0.405083242, 0.094760815, 0.762002269, 0.782725923, 0.657853129),
                 standardError = c(0.824884898, 0.69073481, 0.664255159, 0.099570678, 0.735837865, 0.940523571, 0.933454698, 0.669219927, 0.669924278, 0.537262473))

cft <- tabulator(
  x = dat,
  rows = "row",
  columns = c("question", "column_one","column_two"),
  `P` = as_paragraph(percent),
  `SE` = as_paragraph(standardError)
)

ft <- as_flextable(cft)
ft

I am getting:

Error in melt.data.table(as.data.table(dat), id.vars = c(columns, rows), : One or more values in 'id.vars' is invalid.

Solution

You are not using the table df you created but another named dat that does not contain the column named row.

Here is probably what you wanted to write:

library(flextable)
library(dplyr)

dat <- data.frame(question = c("Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction", "Food Satisfaction"),
                 column_one = c("Portion Size", "Portion Size", "Portion Size", "Portion Size", "Portion Size", "Portion Size", "Region", "Region", "Region", "Region"),
                 column_two = c("Small", "Medium", "Large", "Small", "Medium", "Large", "West", "East", "West", "East"),
                 row = c("Pizza", "Pizza", "Pizza", "Hamburger", "Hamburger", "Hamburger", "Pizza", "Pizza", "Hamburger", "Hamburger"),
                 percent = c(0.83679353, 0.341159874, 0.084278807, 0.071733007, 0.363397833, 0.405083242, 0.094760815, 0.762002269, 0.782725923, 0.657853129),
                 standardError = c(0.824884898, 0.69073481, 0.664255159, 0.099570678, 0.735837865, 0.940523571, 0.933454698, 0.669219927, 0.669924278, 0.537262473))

cft <- tabulator(
  x = dat,
  rows = "row",
  columns = c("question", "column_one","column_two"),
  `P` = as_paragraph(percent),
  `SE` = as_paragraph(standardError)
)

ft <- as_flextable(cft)
ft