multiple kableExtra::column_spec based on number of variables - r

Question

I want to reproduce the figure below for a data frame with any number of columns (assuming all columns have same format)
For example, I have a data frame where each cell is a list containing numeric values
# dataframe containg data
df <- data.frame(YEAR = 1980:1990) %>%
tibble::as_tibble()
vars <- c("a","b","c")
df["a"] <- list(list(rnorm(100)))
df["b"] <- list(list(rnorm(100)))
df["c"] <- list(list(rnorm(100)))
I then create a table
# dataframe to create for table
newdf <- data.frame(YEAR = 1980:1990) %>%
tibble::as_tibble()
newdf[vars] <- ""
# create table
kableExtra::kbl(newdf,
col.names=c("YEAR",vars),
caption=paste0("Title"),
escape=F) %>%
kableExtra::kable_styling(bootstrap_options = c("striped", "hover")) %>%
kableExtra::column_spec(2,image=kableExtra::spec_hist(df$a)) %>%
kableExtra::column_spec(3,image=kableExtra::spec_hist(df$b)) %>%
kableExtra::column_spec(4,image=kableExtra::spec_hist(df$c))
It looks something like this:
This all works great.
However in reality i have a data frame that changes in the number of columns that need to be plotted by kableExtra (since it is created based on user inputs) and i can't work out how to achieve this since in the example above the column_spec function needs to be repeated for each column. So i need a way to generate the table for a variable data frame size.
This seems to be compounded by the use of the pipe operator.
I have looked at piping a function but i think the function still has the same problem of piping a variable number of sequential commands.
Any help greatly appreciated.

Answer 1

You can simultaneously format multiple columns with a purrr::reduce statement, setting the .init argument to the table. That way, the column_spec function can be applied to multiple columns in an elegant way.
The command call will be like
reduce(columns, column_spec, [column_spec arguments], .init = table)
The reduce will call column_spec(table, columns[1], [column_spec arguments], then send that output (call it modified_table) to column_spec(modeifed_table, columns[2], [column_spec arguments], etc.
Here's some example code. Sorry - I tried to create a reprex but I can't get it to work with the html tables.
library(tidyverse)
library(kableExtra)
df <- data.frame(a = 1:10, b = 1:10, c = 1:10)
which_col <- c("b", "c") # which columns to format in the reduce()
df %>%
kbl() %>%
reduce(
which(names(df) %in% which_col), # column_spec wants a vector of column indices
column_spec,
bold = TRUE, # this is a ... argument, which will get sent to column_spec
.init = .
)
# for more complex cases, won't be able to use ... argument as elegantly
df %>%
kbl() %>%
reduce(
which(names(df) %in% which_col),
~column_spec(.x, .y, bold = rep(c(TRUE, FALSE), 5)),
.init = .
)
edit: here is how this would be applied to your table
library(kableExtra)
reduce_inputs <- lst(
col = match(vars, names(newdf)),
dat = df[, vars]
) %>%
transpose()
# create table
newdf %>%
kbl(
newdf,
col.names = c("YEAR", vars),
caption = paste0("Title"),
escape= FALSE
) %>%
kable_styling(bootstrap_options = c("striped", "hover")) %>%
reduce(
reduce_inputs,
~column_spec(.x, .y$col, image = spec_hist(.y$dat)),
.init = .
)