kable indent rows with specific hspace for all columns - r

Question

The following code add indentations to the 2nd & 4th rows for first column only.
library(kableExtra)
knitr::kable(head(mtcars[ ,1:4]), "latex") %>%
add_indent(positions = c(2, 4))
Wondering how to add indentations of specific hspace to the 2nd & 4th rows for all columns. Something like this
library(kableExtra)
knitr::kable(head(mtcars[ ,1:4]), "latex") %>%
add_indent(positions = c(2, 4), hspace = "2em", allCols = TRUE)

Answer 1

add_indent is indeed only made for the first column.
A workaround would be to add the indentation manually in your data frame:
head(mtcars) %>%
mutate_all(., funs(ifelse(row_number() %in% c(2, 4),
paste0("\\hspace{1em}", .), .))) %>%
kable(format = "latex", booktabs = T, escape = F)
gives:

Answer 2

We can write a version of the add_indent function that adds this option. Doing it this way ensures that kable options such as digits are applied consistently in each row.
add_indent = function(kable_input, positions, allCols = FALSE) {
out = kableExtra::add_indent(kable_input, positions)
if (allCols){
table_info <- magic_mirror(kable_input)
for (i in positions + table_info$position_offset) {
rowtext <- table_info$contents[i]
table_info$contents[i] <- gsub(' &', paste(' &', kableExtra:::latex_indent_unit('')), rowtext)
out <- gsub(rowtext, table_info$contents[i], out, fixed = T)
}
out <- structure(out, format = "latex", class = "knitr_kable")
attr(out, "kable_meta") <- table_info
}
return(out)
}
kable(head(mtcars[ ,1:4]), "latex", align = 'l') %>%
add_indent(positions = c(2, 4), allCols = T)