Conditional Formatting of Flextable Correlation Table

Question

I am looking for a way to conditional format a correlation matrix in flextable so that, given a specific value (e.g. .5), cells are highlighted that are above this value. I have looked at previous conditional formatting questions on SO, but have not been able to implement a solution. Here is my reprex, which ends up highlihting all cells:

my_data <- mtcars[, c(1,3,4,5,6,7)] #data
res <- cor(my_data) #initial correlation matrix

res[upper.tri(res)] <- NA # erase the upper triangle
diag(res) <- NA 

res %>%
  as.data.frame() %>%
  rownames_to_column("var") %>%
  flextable::flextable() %>%
  flextable::bg(i = rownames(res) > .5, j = 2:ncol(res), bg = "light blue")

Answer 1

This is a possible solution:

library(flextable)
library(magrittr)
library(tibble)

my_data <- mtcars[, c(1,3,4,5,6,7)] #data
res <- cor(my_data) #initial correlation matrix

res[upper.tri(res)] <- NA # erase the upper triangle
diag(res) <- NA 

res %>%
  as.data.frame() %>%
  rownames_to_column("var") %>%
  flextable::flextable() %>%
  flextable::bg(j = 2:ncol(res), 
                bg = function(x){
                  out <- rep("transparent", length(x))
                  out[x < .5] <- "light blue"
                  out
                })