diff --git a/NAMESPACE b/NAMESPACE
index 8f373128..7cd2f204 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -62,9 +62,7 @@ importFrom(dplyr,tibble)
 importFrom(dplyr,ungroup)
 importFrom(dplyr,vars)
 importFrom(egg,ggarrange)
-importFrom(forcats,fct_rev)
 importFrom(ggplot2,aes)
-importFrom(ggplot2,coord_flip)
 importFrom(ggplot2,element_text)
 importFrom(ggplot2,facet_wrap)
 importFrom(ggplot2,geom_bar)
diff --git a/R/visualize_pathways_level2.R b/R/visualize_pathways_level2.R
index 24d4049f..f4b31327 100644
--- a/R/visualize_pathways_level2.R
+++ b/R/visualize_pathways_level2.R
@@ -8,59 +8,66 @@
 #' @param chosen_pathway_level1 character. A pathway level 1. If CBD standard is
 #'   followed (see argument `cbd_standard`), one of the level 1 pathways from
 #'   `pathways_cbd()`.
-#' @param category NULL or character. One of the kingdoms as given in GBIF and
-#'   `Chordata` (the phylum), `Not Chordata` (all other phyla of `Animalia`): 1.
-#'   `Plantae` 2. `Animalia` 3. `Fungi` 4. `Chromista` 5. `Archaea` 6.
-#'   `Bacteria` 7. `Protozoa` 8. `Viruses` 9. `incertae sedis` 10. `Chordata`
-#'   11. `Not Chordata` Default: `NULL`.
-#' @param from NULL or numeric. Year trade-off: if not \code{NULL} select only
+#' @param category `NULL` (default) or character. One of the kingdoms as given
+#'   in GBIF or `Chordata` (the phylum) or `Not Chordata` (all other phyla of
+#'   `Animalia`):
+#'   1. `Plantae`
+#'   2. `Animalia`
+#'   3. `Fungi`
+#'   4. `Chromista`
+#'   5. `Archaea` 
+#'   6. `Bacteria`
+#'   7. `Protozoa`
+#'   8. `Viruses`
+#'   9. `incertae sedis`
+#'   10. `Chordata`
+#'   11. `Not Chordata`
+#' @param from `NULL` or numeric. Year trade-off: if not `NULL` select only
 #'   pathways related to taxa introduced during or after this year. Default:
 #'   `NULL`.
-#' @param facet_column NULL or character. The column to use to create additional
-#'   facet wrap bar graphs underneath the main graph. When NULL, no facet graph
-#'   are created. One of `family`, `order`, `class`, `phylum`, `locality`,
-#'   `native_range`, `habitat`. If column has another name, rename it before
-#'   calling this function. Default: `NULL`.
-#' @param pathway_level1_names character. Name of the column of \code{df}
+#' @param facet_column `NULL` or character. The column to use to create
+#'   additional facet wrap bar graphs underneath the main graph. When `NULL`, no
+#'   facet graph are created. One of `family`, `order`, `class`, `phylum`,
+#'   `locality`, `native_range`, `habitat`. If column has another name, rename
+#'   it before calling this function. Default: `NULL`.
+#' @param pathway_level1_names character. Name of the column of `df`
 #'   containing information about pathways at level 1. Default:
 #'   `pathway_level1`.
-#' @param pathway_level2_names character. Name of the column of \code{df}
+#' @param pathway_level2_names character. Name of the column of `df`
 #'   containing information about pathways at level 2. Default:
 #'   `pathway_level2`.
 #' @param pathways character. Vector with pathways level 2 to visualize. The
 #'   pathways are displayed following the order as in this vector.
-#' @param taxon_names character. Name of the column of \code{df} containing
+#' @param taxon_names character. Name of the column of `df` containing
 #'   information about taxa. This parameter is used to uniquely identify taxa.
-#' @param kingdom_names character. Name of the column of \code{df} containing
-#'   information about kingdom. Default: \code{"kingdom"}.
-#' @param phylum_names character. Name of the column of \code{df} containing
-#'   information about phylum. This parameter is used only if \code{category} is
-#'   one of:  \code{"Chordata"}, \code{"Not Chordata"}.  Default:
-#'   \code{"phylum"}.
-#' @param first_observed character. Name of the column of \code{df} containing
-#'   information about year of introduction. Default: \code{"first_observed"}.
-#' @param cbd_standard logical. If TRUE the values of pathway level 2 are
+#' @param kingdom_names character. Name of the column of `df` containing
+#'   information about kingdom. Default: `"kingdom"`.
+#' @param phylum_names character. Name of the column of `df` containing
+#'   information about phylum. This parameter is used only if `category` is
+#'   one of: `"Chordata"`, `"Not Chordata"`.  Default:
+#'   `"phylum"`.
+#' @param first_observed character. Name of the column of `df` containing
+#'   information about year of introduction. Default: `"first_observed"`.
+#' @param cbd_standard logical. If `TRUE` the values of pathway level 2 are
 #'   checked based on CBD standard as returned by `pathways_cbd()`. Error is
-#'   returned if unmatched values are found. If FALSE, a warning is returned.
-#'   Default: TRUE.
-#' @param title NULL or character. Title of the graph. Default: NULL.
-#' @param x_lab NULL or character. x-axis label. Default: "Number of introduced
-#'   taxa".
-#' @param y_lab NULL or character. Title of the graph. Default: "Pathways".
-#' @return A ggplot2 object (or egg object if facets are used). NULL if there are
-#'  no data to plot.
+#'   returned if unmatched values are found. If `FALSE`, a warning is returned.
+#'   Default: `TRUE`.
+#' @param title `NULL` or character. Title of the graph. Default: `NULL`.
+#' @param x_lab `NULL` or character. x-axis label. Default: `"Number of
+#'   introduced taxa"`.
+#' @param y_lab `NULL` or character. Title of the graph. Default: `"Pathways"`.
+#' @return A list with three slots:
+#' - `plot`: ggplot2 object (or egg object if facets are used). `NULL` if there
+#' are no data to plot.
+#' - `data_top_graph`: data.frame (tibble) with data used for the main plot (top
+#' graph) in `plot`.
+#' - `data_facet_graph`: data.frame (tibble) with data used for the faceting
+#' plot in `plot`. `NULL` is returned if `facet_column` is `NULL`.
 #'
 #' @export
-#' @importFrom assertthat assert_that
-#' @importFrom assertable assert_colnames
-#' @importFrom dplyr %>% anti_join distinct filter if_else mutate pull rename_at
-#'   sym
-#' @importFrom ggplot2 ggplot geom_bar theme ggtitle xlab ylab coord_flip
-#'   facet_wrap
-#' @importFrom tidyselect all_of
-#' @importFrom forcats fct_rev
+#' 
+#' @importFrom dplyr %>%
 #' @importFrom rlang !!
-#' @importFrom egg ggarrange
 #'
 #' @examples
 #' \dontrun{
@@ -70,36 +77,35 @@
 #'   "interim/data_input_checklist_indicators.tsv"
 #' )
 #' data <- read_tsv(datafile,
-#'   na = "NA",
+#'   na = "",
 #'   col_types = cols(
 #'     .default = col_character(),
 #'     key = col_double(),
 #'     nubKey = col_double(),
 #'     speciesKey = col_double(),
-#'     acceptedKey = col_double(),
 #'     first_observed = col_double(),
 #'     last_observed = col_double()
 #'   )
 #' )
 #' # All taxa
-#' visualize_pathways_level2(t, chosen_pathway_level1 = "escape")
+#' visualize_pathways_level2(data, chosen_pathway_level1 = "escape")
 #'
 #' # Animalia
-#' visualize_pathways_level2(t,
+#' visualize_pathways_level2(data,
 #'   chosen_pathway_level1 = "escape",
 #'   category = "Animalia"
 #' )
 #'
 #' # Chordata
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   category = "Chordata"
 #' )
 #'
 #' # facet phylum
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   category = "Animalia",
 #'   facet_column = "phylum"
@@ -107,21 +113,21 @@
 #'
 #' # facet habitat
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   facet_column = "habitat"
 #' )
 #'
 #' # Only taxa introduced from 1950
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   from = 1950
 #' )
 #'
 #' # Add a title
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   category = "Plantae",
 #'   from = 1950,
@@ -130,7 +136,7 @@
 #'
 #' # Personalize axis labels
 #' visualize_pathways_level2(
-#'   df = t,
+#'   df = data,
 #'   chosen_pathway_level1 = "escape",
 #'   x_lab = "Aantal taxa",
 #'   y_lab = "pathways"
@@ -155,59 +161,65 @@ visualize_pathways_level2 <- function(df,
 
   # initial input checks
   # Check df
-  assert_that(is.data.frame(df), msg = "`df` must be a data frame.")
+  assertthat::assert_that(is.data.frame(df), msg = "`df` must be a data frame.")
   # Check pathway_level1_names
-  assert_that(is.character(pathway_level1_names),
+  assertthat::assert_that(is.character(pathway_level1_names),
     msg = "`pathway_level1_names` must be a character."
   )
-  assert_colnames(df, pathway_level1_names, only_colnames = FALSE)
+  assertthat::assert_that(length(pathway_level1_names) == 1)
+  assertable::assert_colnames(df, pathway_level1_names, only_colnames = FALSE)
   # Check pathway_level2_names
-  assert_that(is.character(pathway_level2_names),
+  assertthat::assert_that(is.character(pathway_level2_names),
     msg = "`pathway_level2_names` must be a character."
   )
-  assert_colnames(df, pathway_level2_names, only_colnames = FALSE)
+  assertthat::assert_that(length(pathway_level2_names) == 1)
+  assertable::assert_colnames(df, pathway_level2_names, only_colnames = FALSE)
   # Check category
   if (!is.null(category)) {
-    assert_that(is.character(category),
+    valid_categories <- c("Chordata", "Not Chordata", "Plantae", "Animalia",
+                          "Fungi", "Chromista", "Archaea", "Bacteria",
+                          "Protozoa", "Viruses", "incertae sedis")
+    assertthat::assert_that(is.character(category),
       msg = paste0(
-        "`category` must be a character. One of: ",
-        paste(categories, collapse = ", "),
+        "`category` must be NULL or a character. One of: ",
+        paste(valid_categories, collapse = ", "),
         "."
       )
     )
-    assert_that(category %in% categories,
+    assertthat::assert_that(length(category) == 1)
+    assertthat::assert_that(category %in% valid_categories,
       msg = paste0(
         "`category` is not correct. Choose one of: ",
-        paste0(categories, collapse = ", "),
+        paste0(valid_categories, collapse = ", "),
         "."
       )
     )
   }
   # Check facet_column
-  assert_that(is.null(facet_column) | is.character(facet_column),
+  assertthat::assert_that(is.null(facet_column) | is.character(facet_column),
     msg = "Argument facet_column has to be NULL or a character."
   )
   if (is.character(facet_column)) {
-    assert_colnames(df, facet_column, only_colnames = FALSE)
-  }
-  # check for valid facet options
-  valid_facet_options <- c(
-    "family", "order", "class", "phylum",
-    "locality", "native_range", "habitat"
-  )
-  if (is.character(facet_column)) {
-    facet_column <- match.arg(facet_column, valid_facet_options)
-    assert_that(is.null(category) || !(category == "Chordata" &
+    assertthat::assert_that(length(facet_column) == 1)
+    assertable::assert_colnames(df, facet_column, only_colnames = FALSE)
+    # check facet column
+    valid_facets <- c(
+      "family", "order", "class", "phylum",
+      "locality", "native_range", "habitat"
+    )
+    facet_column <- match.arg(facet_column, valid_facets)
+    assertthat::assert_that(is.null(category) || !(category == "Chordata" &
       facet_column == "phylum"),
     msg = "You cannot use phylum as facet with category Chordata."
     )
   }
   # Check chosen_pathway_level1
-  assert_that(is.character(chosen_pathway_level1),
+  assertthat::assert_that(is.character(chosen_pathway_level1),
     msg = "Argument `chosen_pathway_level1` must be a character."
   )
+  assertthat::assert_that(length(chosen_pathway_level1) == 1)
   pathways_level1 <- unique(df[[pathway_level1_names]])
-  assert_that(chosen_pathway_level1 %in% pathways_level1,
+  assertthat::assert_that(chosen_pathway_level1 %in% pathways_level1,
     msg = paste0(
       "chosen_pathway_level1 ",
       chosen_pathway_level1,
@@ -218,12 +230,13 @@ visualize_pathways_level2 <- function(df,
   )
   # Check pathways
   if (!is.null(pathways)) {
-    assert_that(is.character(pathways),
+    assertthat::assert_that(is.character(pathways),
       msg = "`pathways` must be a vector of characters."
     )
+    assertthat::assert_that(length(pathways) == 1)
     invalid_pathways <- pathways[!pathways %in%
       df[[pathway_level2_names]]]
-    assert_that(length(invalid_pathways) == 0,
+    assertthat::assert_that(length(invalid_pathways) == 0,
       msg = paste0(
         "Pathways in `pathways` not present in ",
         "data.frame: ",
@@ -233,32 +246,37 @@ visualize_pathways_level2 <- function(df,
     )
   }
   # Check taxon_names
-  assert_that(is.character(taxon_names),
+  assertthat::assert_that(is.character(taxon_names),
     msg = "`taxon_names` must be a character."
   )
-  assert_colnames(df, taxon_names, only_colnames = FALSE)
+  assertthat::assert_that(length(taxon_names) == 1)
+  assertable::assert_colnames(df, taxon_names, only_colnames = FALSE)
   # Check kingdom_names
-  assert_that(is.character(kingdom_names),
+  assertthat::assert_that(is.character(kingdom_names),
     msg = "`kingdom_names` must be a character."
   )
-  assert_colnames(df, kingdom_names, only_colnames = FALSE)
+  assertthat::assert_that(length(kingdom_names) == 1)
+  assertable::assert_colnames(df, kingdom_names, only_colnames = FALSE)
   # check parameter phylum
-  assert_that(is.character(phylum_names),
+  assertthat::assert_that(is.character(phylum_names),
     msg = "`phylum_names` must be a character."
   )
-  assert_colnames(df, phylum_names, only_colnames = FALSE)
+  assertthat::assert_that(length(phylum_names) == 1)
+  assertable::assert_colnames(df, phylum_names, only_colnames = FALSE)
   # Check from
   if (!is.null(from)) {
-    assert_that(is.numeric(from),
+    assertthat::assert_that(is.numeric(from),
       msg = "`from` must be a number (year)."
     )
-    assert_that(from > 0,
+    assertthat::assert_that(length(from) == 1)
+    assertthat::assert_that(from > 0,
       msg = "`from` must be a positive number."
     )
-    assert_that(from == as.integer(from),
+    assertthat::assert_that(from == as.integer(from),
       msg = "`from` must be an integer."
     )
-    assert_that(from <= as.numeric(substr(Sys.Date(), start = 1, stop = 4)),
+    assertthat::assert_that(
+      from <= as.numeric(substr(Sys.Date(), start = 1, stop = 4)),
       msg = paste0(
         "`from` must be less than ",
         format(Sys.Date(), "%Y"),
@@ -267,53 +285,56 @@ visualize_pathways_level2 <- function(df,
     )
   }
   # Check first_observed
-  assert_that(is.character(first_observed),
+  assertthat::assert_that(is.character(first_observed),
     msg = "`first_observed` must be a character."
   )
-  assert_colnames(df, first_observed, only_colnames = FALSE)
+  assertthat::assert_that(length(first_observed) == 1)
+  assertable::assert_colnames(df, first_observed, only_colnames = FALSE)
   # Check title and labels
   if (!is.null(title)) {
-    assert_that(is.character(title),
+    assertthat::assert_that(is.character(title),
       msg = "`title` must be a character or NULL."
     )
+    assertthat::assert_that(length(title) == 1)
   }
   if (!is.null(x_lab)) {
-    assert_that(is.character(x_lab),
+    assertthat::assert_that(is.character(x_lab),
       msg = "`x_lab` must be a character or NULL."
     )
   }
   if (!is.null(y_lab)) {
-    assert_that(is.character(y_lab),
+    assertthat::assert_that(is.character(y_lab),
       msg = "`y_lab` must be a character or NULL."
     )
+    assertthat::assert_that(length(y_lab) == 1)
   }
   # rename to default column name
   df <-
     df %>%
-    rename_at(vars(all_of(kingdom_names)), ~"group") %>%
-    rename_at(vars(all_of(taxon_names)), ~"taxonKey") %>%
-    rename_at(vars(all_of(first_observed)), ~"first_observed") %>%
-    rename_at(vars(all_of(pathway_level1_names)), ~"pathway_level1") %>%
-    rename_at(vars(all_of(pathway_level2_names)), ~"pathway_level2")
+    dplyr::rename_at(vars(tidyselect::all_of(kingdom_names)), ~"group") %>%
+    dplyr::rename_at(vars(tidyselect::all_of(taxon_names)), ~"taxonKey") %>%
+    dplyr::rename_at(vars(tidyselect::all_of(first_observed)), ~"first_observed") %>%
+    dplyr::rename_at(vars(tidyselect::all_of(pathway_level1_names)), ~"pathway_level1") %>%
+    dplyr::rename_at(vars(tidyselect::all_of(pathway_level2_names)), ~"pathway_level2")
   # Select data with the chosen pathway level 1
   df <-
     df %>%
-    filter(.data$pathway_level1 == chosen_pathway_level1)
+    dplyr::filter(.data$pathway_level1 == chosen_pathway_level1)
   # handle asymmetric category system (Chordata, Not Chordta are not kingdoms)
   if (!is.null(category)) {
     if (!category %in% c("Chordata", "Not Chordata")) {
-      df <- df %>% filter(.data$group == category)
+      df <- df %>% dplyr::filter(.data$group == category)
     } else {
       df <-
         df %>%
-        rename_at(vars(phylum_names), ~"phylum_group")
+        dplyr::rename_at(vars(phylum_names), ~"phylum_group")
       if (category == "Chordata") {
-        df <- df %>% filter(.data$phylum_group == category)
+        df <- df %>% dplyr::filter(.data$phylum_group == category)
       } else {
         df <-
           df %>%
-          filter(.data$group == "Animalia") %>%
-          filter(.data$phylum_group != "Chordata")
+          dplyr::filter(.data$group == "Animalia") %>%
+          dplyr::filter(.data$phylum_group != "Chordata")
       }
     }
   }
@@ -321,14 +342,14 @@ visualize_pathways_level2 <- function(df,
   if (!is.null(from)) {
     df <-
       df %>%
-      filter(.data$first_observed >= from)
+      dplyr::filter(.data$first_observed >= from)
   }
   # Handle NAs and ""
   nas_or_empty_pathway_level2 <-
     df %>%
-    filter(is.na(.data$pathway_level2) |
+    dplyr::filter(is.na(.data$pathway_level2) |
       .data$pathway_level2 == "") %>%
-    distinct(.data$taxonKey)
+    dplyr::distinct(.data$taxonKey)
   if (nrow(nas_or_empty_pathway_level2) > 0) {
     message_warning <- paste(
       nrow(nas_or_empty_pathway_level2),
@@ -340,7 +361,7 @@ visualize_pathways_level2 <- function(df,
   df <-
     df %>%
     # Handle NAs and "unknown"
-    mutate(pathway_level2 = if_else(is.na(.data$pathway_level2) |
+    dplyr::mutate(pathway_level2 = dplyr::if_else(is.na(.data$pathway_level2) |
       .data$pathway_level2 == "",
     "unknown",
     .data$pathway_level2
@@ -348,18 +369,18 @@ visualize_pathways_level2 <- function(df,
   # Import all CBD pathways level 2 within chosen pathway level 1
   pathways_level2_all <-
     pathways_cbd() %>%
-    filter(.data$pathway_level1 == chosen_pathway_level1) %>%
-    distinct(.data$pathway_level2)
+    dplyr::filter(.data$pathway_level1 == chosen_pathway_level1) %>%
+    dplyr::distinct(.data$pathway_level2)
   # Select pathways
   if (!is.null(pathways)) {
     pathways <- replace(pathways, is.na(pathways) | pathways == "", "unknown")
     pathways <- unique(pathways)
     df <-
       df %>%
-      filter(.data$pathway_level2 %in% pathways)
+      dplyr::filter(.data$pathway_level2 %in% pathways)
   } else {
     if (cbd_standard == TRUE) {
-      pathways <- pathways_level2_all %>% pull()
+      pathways <- pathways_level2_all %>% dplyr::pull()
     } else {
       pathways <- unique(df$pathway_level2)
     }
@@ -367,11 +388,11 @@ visualize_pathways_level2 <- function(df,
   # Check values in column with pathways level 2
   invalid_pathways <-
     df %>%
-    anti_join(pathways_level2_all,
+    dplyr::anti_join(pathways_level2_all,
       by = "pathway_level2"
     ) %>%
-    distinct(.data$pathway_level2) %>%
-    pull()
+    dplyr::distinct(.data$pathway_level2) %>%
+    dplyr::pull()
   message_invalid_pathways <-
     paste0(
       "No CBD standard pathways level 2 value(s) in column `",
@@ -383,65 +404,69 @@ visualize_pathways_level2 <- function(df,
       "."
     )
   if (cbd_standard == TRUE) {
-    assert_that(length(invalid_pathways) == 0,
+    assertthat::assert_that(length(invalid_pathways) == 0,
       msg = message_invalid_pathways
     )
   } else {
     warning(message_invalid_pathways)
   }
-  # Distinct taxa
+  # dplyr::distinct taxa
   if (!is.null(facet_column)) {
     df <-
       df %>%
-      distinct(.data$taxonKey, .data$pathway_level2, !!sym(facet_column))
+      dplyr::distinct(.data$taxonKey, .data$pathway_level2, !!dplyr::sym(facet_column))
   }
   # Transform pathway level 2 column to factor to make ordering in graph easily
   df <-
     df %>%
-    mutate(pathway_level2 = factor(.data$pathway_level2, levels = pathways))
-  # Distinct taxa without facet
-  df_top_graph <-
+    dplyr::mutate(pathway_level2 = factor(.data$pathway_level2, levels = pathways))
+  # dplyr::distinct taxa without facet
+  data_top_graph <-
     df %>%
-    distinct(
+    dplyr::distinct(
       .data$taxonKey,
       .data$pathway_level2
     )
   # Plot number of taxa per pathway_level1
   top_graph <- NULL
-  if (nrow(df_top_graph) > 0) {
+  if (nrow(data_top_graph) > 0) {
     top_graph <-
-      ggplot(
-        df_top_graph,
-        aes(x = fct_rev(.data$pathway_level2))
+      ggplot2::ggplot(
+        data_top_graph,
+        aes(x = forcats::fct_rev(.data$pathway_level2))
       ) +
-      geom_bar() +
-      xlab(y_lab) +
-      ylab(x_lab) +
-      coord_flip() +
-      ggtitle(title)
+      ggplot2::geom_bar() +
+      ggplot2::xlab(y_lab) +
+      ggplot2::ylab(x_lab) +
+      ggplot2::coord_flip() +
+      ggplot2::ggtitle(title)
   }
   if (is.null(facet_column)) {
-    return(top_graph)
+    return(list(plot = top_graph,
+                data_top_graph = data_top_graph,
+                data_facet_graph = NULL))
   } else {
     facet_graph <- NULL
     if (nrow(df) > 0) {
       facet_graph <-
-        ggplot(
+        ggplot2::ggplot(
           df,
-          aes(x = fct_rev(.data$pathway_level2))
+          aes(x = forcats::fct_rev(.data$pathway_level2))
         ) +
-        geom_bar() +
-        xlab(y_lab) + # invert labels to get them right after flipping
-        ylab(x_lab) +
-        coord_flip() +
-        ggtitle(title) +
-        facet_wrap(facet_column)
+        ggplot2::geom_bar() +
+        ggplot2::xlab(y_lab) + # invert labels to get them right after flipping
+        ggplot2::ylab(x_lab) +
+        ggplot2::coord_flip() +
+        ggplot2::ggtitle(title) +
+        ggplot2::facet_wrap(facet_column)
     }
     if (all(!is.null(top_graph), !is.null(facet_graph))) {
-      ggarrange(top_graph, facet_graph)
+      return(list(plot = egg::ggarrange(top_graph, facet_graph),
+                  data_top_graph = data_top_graph,
+                  data_facet_graph = df))
     }
     else {
-      NULL
+      return(list(plot = NULL, data_top_graph = NULL, data_facet_graph = NULL))
     }
   }
 }
diff --git a/man/visualize_pathways_level2.Rd b/man/visualize_pathways_level2.Rd
index e0715cfe..58740fc7 100644
--- a/man/visualize_pathways_level2.Rd
+++ b/man/visualize_pathways_level2.Rd
@@ -30,21 +30,32 @@ visualize_pathways_level2(
 followed (see argument \code{cbd_standard}), one of the level 1 pathways from
 \code{pathways_cbd()}.}
 
-\item{category}{NULL or character. One of the kingdoms as given in GBIF and
-\code{Chordata} (the phylum), \verb{Not Chordata} (all other phyla of \code{Animalia}): 1.
-\code{Plantae} 2. \code{Animalia} 3. \code{Fungi} 4. \code{Chromista} 5. \code{Archaea} 6.
-\code{Bacteria} 7. \code{Protozoa} 8. \code{Viruses} 9. \verb{incertae sedis} 10. \code{Chordata}
-11. \verb{Not Chordata} Default: \code{NULL}.}
-
-\item{from}{NULL or numeric. Year trade-off: if not \code{NULL} select only
+\item{category}{\code{NULL} (default) or character. One of the kingdoms as given
+in GBIF or \code{Chordata} (the phylum) or \verb{Not Chordata} (all other phyla of
+\code{Animalia}):
+\enumerate{
+\item \code{Plantae}
+\item \code{Animalia}
+\item \code{Fungi}
+\item \code{Chromista}
+\item \code{Archaea}
+\item \code{Bacteria}
+\item \code{Protozoa}
+\item \code{Viruses}
+\item \verb{incertae sedis}
+\item \code{Chordata}
+\item \verb{Not Chordata}
+}}
+
+\item{from}{\code{NULL} or numeric. Year trade-off: if not \code{NULL} select only
 pathways related to taxa introduced during or after this year. Default:
 \code{NULL}.}
 
-\item{facet_column}{NULL or character. The column to use to create additional
-facet wrap bar graphs underneath the main graph. When NULL, no facet graph
-are created. One of \code{family}, \code{order}, \code{class}, \code{phylum}, \code{locality},
-\code{native_range}, \code{habitat}. If column has another name, rename it before
-calling this function. Default: \code{NULL}.}
+\item{facet_column}{\code{NULL} or character. The column to use to create
+additional facet wrap bar graphs underneath the main graph. When \code{NULL}, no
+facet graph are created. One of \code{family}, \code{order}, \code{class}, \code{phylum},
+\code{locality}, \code{native_range}, \code{habitat}. If column has another name, rename
+it before calling this function. Default: \code{NULL}.}
 
 \item{pathways}{character. Vector with pathways level 2 to visualize. The
 pathways are displayed following the order as in this vector.}
@@ -65,27 +76,33 @@ information about kingdom. Default: \code{"kingdom"}.}
 
 \item{phylum_names}{character. Name of the column of \code{df} containing
 information about phylum. This parameter is used only if \code{category} is
-one of:  \code{"Chordata"}, \code{"Not Chordata"}.  Default:
+one of: \code{"Chordata"}, \code{"Not Chordata"}.  Default:
 \code{"phylum"}.}
 
 \item{first_observed}{character. Name of the column of \code{df} containing
 information about year of introduction. Default: \code{"first_observed"}.}
 
-\item{cbd_standard}{logical. If TRUE the values of pathway level 2 are
+\item{cbd_standard}{logical. If \code{TRUE} the values of pathway level 2 are
 checked based on CBD standard as returned by \code{pathways_cbd()}. Error is
-returned if unmatched values are found. If FALSE, a warning is returned.
-Default: TRUE.}
+returned if unmatched values are found. If \code{FALSE}, a warning is returned.
+Default: \code{TRUE}.}
 
-\item{title}{NULL or character. Title of the graph. Default: NULL.}
+\item{title}{\code{NULL} or character. Title of the graph. Default: \code{NULL}.}
 
-\item{x_lab}{NULL or character. x-axis label. Default: "Number of introduced
-taxa".}
+\item{x_lab}{\code{NULL} or character. x-axis label. Default: \code{"Number of introduced taxa"}.}
 
-\item{y_lab}{NULL or character. Title of the graph. Default: "Pathways".}
+\item{y_lab}{\code{NULL} or character. Title of the graph. Default: \code{"Pathways"}.}
 }
 \value{
-A ggplot2 object (or egg object if facets are used). NULL if there are
-no data to plot.
+A list with three slots:
+\itemize{
+\item \code{plot}: ggplot2 object (or egg object if facets are used). \code{NULL} if there
+are no data to plot.
+\item \code{data_top_graph}: data.frame (tibble) with data used for the main plot (top
+graph) in \code{plot}.
+\item \code{data_facet_graph}: data.frame (tibble) with data used for the faceting
+plot in \code{plot}. \code{NULL} is returned if \code{facet_column} is \code{NULL}.
+}
 }
 \description{
 Function to plot bar graph with number of taxa introduced by different