kable code example
Example 1: options kable NA
options(knitr.kable.NA = '')
Example 2: kable column names
require(knitr)
df <- data.frame(A=c(1,2),B=c(4,2),C=c(3,4),D=c(8,7))
knitr::kable(df,
col.names = c("Space in name",
"(Special Characters)",
"$\\delta{m}_1$",
"Space in name"))