refactor bar_plot_fractions and add error handling

DESCRIPTION

@@ -19,6 +19,7 @@ Imports:
     lubridate,
     pbapply,
     purrr,
+    rlang,
     rvest,
     stringr,
     tibble,

R/analyze.R

@@ -78,17 +78,17 @@ party_order <- factor(c("Fraktionslos", "AfD&Fraktionslos",
 #' 
 #' @export
 bar_plot_fractions <- function(tb,
-                                x_variable = NULL, # default is fraction
-                                y_variable = NULL, # default is n
-                                fill = NULL, # default is fraction
-                                title = NULL,
-                                xlab = "Fraction",
-                                ylab = "n",
-                                filllab = "Fraction",
-                                flipped = TRUE,
-                                position = "dodge",
-                                reorder = FALSE,
-                                rotatelab = FALSE) {
+                               x_variable = NULL, # default is fraction
+                               y_variable = NULL, # default is n
+                               fill = NULL, # default is fraction
+                               title = NULL,
+                               xlab = "Fraction",
+                               ylab = "n",
+                               filllab = "Fraction",
+                               flipped = TRUE,
+                               position = "dodge",
+                               reorder = FALSE,
+                               rotatelab = FALSE) {
     # capture expressions in arguments
     fill <- enexpr(fill)
     y_variable <- enexpr(y_variable)
@@ -99,6 +99,29 @@ bar_plot_fractions <- function(tb,
     if (is.null(y_variable)) y_variable <- expr(n)
     if (is.null(x_variable)) x_variable <- expr(fraction)
 
+    # check if variables exist
+    if (!rlang::expr_text(x_variable) %in% names(tb))
+        stop(paste0(rlang::expr_text(x_variable),
+                    " is not a column of tb. Did you set x_variable accordingly?"),
+             .call = NULL)
+    if (!rlang::expr_text(y_variable) %in% names(tb))
+        stop(paste0(rlang::expr_text(y_variable),
+                    " is not a column of tb. Did you set y_variable accordingly?"),
+             .call = NULL)
+    if (!rlang::expr_text(fill) %in% names(tb))
+        stop(paste0(rlang::expr_text(fill),
+                    " is not a column of tb. Did you set fill accordingly?"),
+             .call = NULL)
+
+    # check argument types
+    stopifnot("title has to be of type character or NULL" = is.character(title) || is.null(title))
+    stopifnot("xlab has to be of type character" = is.character(xlab))
+    stopifnot("ylab has to be of type character" = is.character(ylab))
+    stopifnot("filllab has to be of type character" = is.character(filllab))
+    stopifnot("flipped has to be of type logical" = is.logical(flipped))
+    stopifnot("rotatelab has to be of type logical" = is.logical(rotatelab))
+    stopifnot("reorder has to be of type logical" = is.logical(reorder))
+
     # either reorder fraction factor by variable value
     if (reorder) maps <- aes(x = reorder(!!x_variable, -!!y_variable),
                              y = !!y_variable,
@@ -108,22 +131,8 @@ bar_plot_fractions <- function(tb,
                      y = !!y_variable,
                      fill = factor(!!fill, levels = party_order))
     
-    if(rotatelab){
     # make a bar plot
-    ggplot(tb, maps, rotate) +
-        scale_fill_manual(values = party_colors, na.value = "#555555") +
-        xlab(xlab) +
-        ylab(ylab) +
-        labs(fill = filllab) +
-        ggtitle(title) +
-        geom_bar(stat = "identity", position = position) + 
-        theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1)) ->
-        plt
-    }
-
-    else{
-      # make a bar plot
-      ggplot(tb, maps, rotate) +
+    ggplot(tb, maps) +
         scale_fill_manual(values = party_colors, na.value = "#555555") +
         xlab(xlab) +
         ylab(ylab) +
@@ -131,7 +140,10 @@ bar_plot_fractions <- function(tb,
         ggtitle(title) +
         geom_bar(stat = "identity", position = position) ->
         plt
-    }
+
+    # if rotatelab == TRUE, rotate x labels by 90 degrees
+    if (rotatelab)
+        plt + theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1)) -> plt
     
     # if flipped == TRUE, draw bars horizontally (default TRUE)
     if (flipped) plt + coord_flip() else plt