diff --git a/R/add_header_left.R b/R/add_header_left.R
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+#' Add a heading column to the left side of the table
+#'
+#' @description This function uses the same syntax as add_header_above. It will
+#' add a heading column with grouped rows to the left side of the table. It can
+#' act as an alternative way to `group_rows` to show grouped information. As
+#' `add_header_above`, users can use this function to add multiple layers of
+#' heading columns one by one.
+#'
+#' @param kable_input Output of `knitr::kable()` with `format` specified
+#' @param header A (named) character vector with `rowspan` as values. For
+#' example, `c("xxx" = 1, "title" = 2)` can be used to create a new header column
+#' for a 3-row table with "xxx" spanning row 1 and "title" spanning row 2 & 3 (
+#' two rows). For convenience, when `rowspan` equals to 1, users can drop the
+#' ` = 1` part. As a result, `c("xxx", "title" = 2)` is the same as
+#' `c("xxx" = 1, "title" = 2)`.
+#' @param header_name Column name that that extra column
+#' @param width A character string for the width of the new column. Values
+#' could be "10cm", "3in" or "30em", etc..
+#' @param align Column alignment. you can choose from "c", "l" or "r"
+#' @param bold A T/F value to control whether the text should be bolded.
+#' @param italic A T/F value to control whether the text should to be emphasized.
+#' @param ... Extra options to be passed into HTML or LaTeX. Right now there is
+#' only one for LaTeX. Option full_midline is a TRUE/FALSE option to control
+#' if the mid line needs to be extended to the end of row.
+#'
+#' @examples x <- knitr::kable(head(mtcars), "html")
+#' add_header_left(x, c("A" = 2, "B" = 2, "C" = 2))
+add_header_left <- function(kable_input, header = NULL, header_name = "",
+                            align = "c", width = NULL, bold = F, italic = F,
+                            ...) {
+  if (is.null(header)) return(kable_input)
+  kable_format <- attr(kable_input, "format")
+  if (!kable_format %in% c("html", "latex")) {
+    stop("Please specify output format in your kable function. Currently ",
+         "generic markdown table using pandoc is not supported.")
+  }
+  if (kable_format == "html") {
+    return(add_header_left_html(kable_input, header, header_name, align,
+                                width, bold, italic))
+  }
+  if (kable_format == "latex") {
+    return(add_header_left_latex(kable_input, header, header_name, align,
+                                 width, bold, italic, ...))
+  }
+}
+
+# HTML
+add_header_left_html <- function(kable_input, header, header_name, align,
+                                 width, bold, italic) {
+  kable_attrs <- attributes(kable_input)
+  kable_xml <- read_xml(as.character(kable_input), options = "COMPACT")
+  kable_thead <- xml_tpart(kable_xml, "thead")
+  kable_tbody <- xml_tpart(kable_xml, "tbody")
+
+  align <- match.arg(align, c("c", "l", "r"))
+  align <- switch(align, "c" = "center", "l" = "left", "r" = "right")
+
+  column_style <- paste0(
+    ifelse(!is.null(width), paste0("width: ", width, "; "), ""),
+    ifelse(bold, "font-weight: bold; ", ""),
+    ifelse(italic, "font-style: italic; ", "")
+  )
+
+  new_header <- paste0(
+    '<th style="text-align:', align, '; vertical-align: bottom;', column_style,
+    '" rowspan="', length(xml_children(kable_thead)), '">', header_name, '</th>'
+  )
+  new_header <- read_xml(new_header, options = c("COMPACT"))
+  xml_add_child(xml_child(kable_thead, 1), new_header, .where = 0)
+
+  header <- standardize_header(header, length(xml_children(kable_tbody)))
+  for (i in 1:nrow(header)) {
+    new_row_item <- paste0(
+      '<td style="text-align:', align, '; vertical-align: middle;',
+      column_style, '" rowspan="',
+      header$rowspan[i], '">', header$header[i], '</td>')
+    new_row_item <- read_xml(new_row_item, options = "COMPACT")
+    target_row <- xml_child(kable_tbody, header$row[i])
+    xml_add_child(target_row, new_row_item, .where = 0)
+  }
+
+  out <- structure(as.character(kable_xml), format = "html",
+                   class = "knitr_kable")
+
+  # Adjust for column_spec
+  if (is.null(kable_attrs$column_adjust)) {
+    table_nrow <- length(xml_children(kable_tbody))
+    # if (!is.null(kable_attrs$group_header_rows)) {
+    #   table_nrow <- table_nrow - length(kable_attrs$group_header_rows)
+    # }
+    table_ncol <- length(xml_children(
+      xml_child(kable_thead, length(xml_children(kable_thead)))
+    ))
+    kable_attrs$column_adjust$matrix <- matrix(
+      rep(TRUE, table_nrow * table_ncol), ncol = table_nrow)
+    kable_attrs$column_adjust$count <- 1
+    new_row_index <- rep(FALSE, table_nrow)
+  } else {
+    new_row_index <- rep(FALSE, ncol(kable_attrs$column_adjust$matrix))
+    kable_attrs$column_adjust$count <- 1 + kable_attrs$column_adjust$count
+  }
+  new_row_index[header$row] <- TRUE
+  kable_attrs$column_adjust$matrix <- rbind(
+    new_row_index, kable_attrs$column_adjust$matrix
+  )
+  attributes(out) <- kable_attrs
+
+  return(out)
+}
+
+standardize_header <- function(header, n_row) {
+  header_names <- names(header)
+
+  if (is.null(header_names)) {
+    return(data.frame(header = header, row = 1:length(header),
+                      rowspan = 1, row.names = NULL))
+  }
+
+  names(header)[header_names == ""] <- header[header_names == ""]
+  header[header_names == ""] <- 1
+  header_names <- names(header)
+  header <- as.numeric(header)
+  names(header) <- header_names
+  if (sum(header) < n_row) {
+    header <- c(header, " " = n_row - sum(header))
+  }
+  row_pos <- c(1, cumsum(header)[-length(header)] + 1)
+  return(data.frame(
+    header = names(header),
+    row = row_pos, rowspan = header, row.names = NULL
+    ))
+}
+
+add_header_left_latex <- function(kable_input, header, header_name, align,
+                                  width, bold, italic, full_midline = F) {
+  table_info <- magic_mirror(kable_input)
+  usepackage_latex("multirow")
+  if (!table_info$booktabs) {
+    warning("add_header_left only supports LaTeX table with booktabs. Please",
+            " use kable(..., booktabs = T) in your kable function.")
+  }
+  out <- as.character(kable_input)
+  contents <- table_info$contents
+  header_name <- escape_latex(header_name)
+  header <- standardize_header(header, length(contents) - 1)
+  header$header <- escape_latex(header$header)
+  header$header <- gsub("\\\\", "\\\\\\\\", header$header)
+  header$row <- header$row + 1
+  header$row_end <- header$row + header$rowspan - 1
+
+  # Align
+  align_row <- latex_column_align_builder(align, width, bold, italic)
+
+  out <- sub(paste0(table_info$begin_tabular, "\\{"),
+             paste0(table_info$begin_tabular, "{", align_row,
+                    ifelse(table_info$booktabs, "", "|")),
+             out, perl = T)
+  # table_info$align_vector <- c(align, table_info$align_vector)
+
+  # Header
+  ## Extra header rows introduced by add_header_above
+  if (!is.null(table_info$new_header_row)) {
+    new_header_row <- table_info$new_header_row
+    for (i in 1:length(new_header_row)) {
+      out <- sub(regex_escape(new_header_row[i]),
+                 paste0(" & ", new_header_row[i]), out)
+      cline_old <- cline_gen(table_info$header_df[[i]], table_info$booktabs)
+      cline_old <- regex_escape(cline_old)
+      table_info$header_df[[i]] <- rbind(
+        data.frame(header = " ", colspan = 1),
+        table_info$header_df[[i]]
+      )
+      cline_new <- cline_gen(table_info$header_df[[i]], table_info$booktabs)
+      out <- sub(cline_old, cline_new, out)
+    }
+  }
+  ## Base Header row
+  out <- sub(contents[1], paste0(header_name, " & ", contents[1]), out)
+  table_info$contents[1] <- paste0(header_name, " & ", contents[1])
+
+  # move existing midrules if exists
+  out_lines <- read_lines(out)
+  tbody_start_row <- which(out_lines == "\\midrule")
+  tbody_end_row <- which(out_lines == "\\bottomrule")
+  before_tbody <- out_lines[seq(1, tbody_start_row)]
+  tbody <- out_lines[seq(tbody_start_row + 1, tbody_end_row - 1)]
+  after_tbody <- out_lines[seq(tbody_end_row, length(out_lines))]
+
+  # Remove addlinespace in this case
+  tbody <- tbody[tbody != "\\addlinespace"]
+
+  midrule_exist <- str_sub(tbody, 1, 9) == "\\cmidrule"
+  if (sum(midrule_exist) > 0) {
+    existing_midrules <- which(midrule_exist)
+    tbody[existing_midrules] <- unlist(lapply(
+      tbody[existing_midrules], cmidrule_plus_one
+    ))
+    out <- paste0(c(before_tbody, tbody, after_tbody), collapse = "\n")
+  }
+
+  for (j in 1:nrow(header)) {
+    new_row_pre <- paste0(
+      "\\\\multirow\\{", -header$rowspan[j], "\\}\\{",
+      ifelse(is.null(width), "\\*", width),
+      "\\}\\{",
+      switch(align,
+             "l" = "\\\\raggedright\\\\arraybackslash ",
+             "c" = "\\\\centering\\\\arraybackslash ",
+             "r" = "\\\\raggedleft\\\\arraybackslash "),
+      header$header[j], "\\} & "
+    )
+    new_row_text <- paste0(new_row_pre, contents[header$row_end[j]])
+    out <- sub(contents[header$row_end[j]], new_row_text, out)
+    table_info$contents[header$row_end[j]] <- new_row_text
+    if (j != nrow(header)) {
+      out <- sub(
+        paste0(contents[header$row_end[j]], "\\\\\\\\\n"),
+        paste0(contents[header$row_end[j]],
+               "\\\\\\\\\n\\\\cmidrule[0.5pt](l{2pt}r{2pt}){1-",
+               ifelse(full_midline, str_count(tbody[1], " & ") + 2, 1),
+               "}\n"),
+        out
+      )
+    }
+  }
+
+  for (k in setdiff(seq(2, length(contents)), header$row_end)) {
+    out <- sub(contents[k],
+               paste0("  & ", contents[k]),
+               out)
+    table_info$contents[k] <- paste0("  & ", contents[k])
+  }
+
+  out <- structure(out, format = "latex", class = "knitr_kable")
+
+  attr(out, "kable_meta") <- table_info
+  return(out)
+}
+
+cmidrule_plus_one <- function(x) {
+  start_pos <- as.numeric(str_match(x, "\\)\\{(.*)-")[2]) + 1
+  stop_pos <- as.numeric(str_match(x, "-(.*)\\}")[2]) + 1
+  return(
+    paste0("\\cmidrule[0.5pt](l{2pt}r{2pt}){", start_pos, "-", stop_pos, "}")
+  )
+}