adding none to add_footnote
diff --git a/R/add_footnote.R b/R/add_footnote.R
index feb1269..49e37cb 100644
--- a/R/add_footnote.R
+++ b/R/add_footnote.R
@@ -7,7 +7,7 @@
 #' @param label A vector of footnotes you want to add. You don't need to add
 #' notations in your notes.
 #' @param notation You can select the format of your footnote notation from
-#' `number`, `alphabet` and `symbol`.
+#' `number`, `alphabet`, `symbol` and `none`.
 #' @param threeparttable Boolean value indicating if a
 #' \href{https://www.ctan.org/pkg/threeparttable}{threeparttable} scheme should
 #' be used.
@@ -31,16 +31,22 @@
     threeparttable <- getOption("kable_footnote_threeparttable", FALSE)
   }
 
-  notation <- match.arg(notation, c("alphabet", "number", "symbol"))
-  if (notation == "symbol") {
-    notation <- paste0(notation, ".", attr(input, "format"))
-  }
-
   table_info <- NULL
 
-  ids.ops <- read.csv(system.file("symbol_index.csv", package = "kableExtra"))
-  ids <- ids.ops[, notation]
-  ids.intable <- gsub("\\*", "\\\\*", ids)
+  notation <- match.arg(notation, c("alphabet", "number", "symbol", "none"))
+  if (notation == "none") {
+    ids <- rep("", 20)
+    ids.intable <- ids
+  } else {
+    if (notation == "symbol") {
+      notation <- paste0(notation, ".", attr(input, "format"))
+    }
+
+    ids.ops <- read.csv(system.file("symbol_index.csv", package = "kableExtra"))
+    ids <- ids.ops[, notation]
+    ids.intable <- gsub("\\*", "\\\\*", ids)
+  }
+
 
   #count the number of items in label and intable notation
   count.label <- length(label)