adds geom_density

This commit contains everything required to add a new geom (geom_density).

src/TidierPlots.jl

@@ -16,6 +16,7 @@ include("geom_bar.jl")
 include("geom_boxplot.jl")
 include("geom_contour.jl")
 include("geom_errorbar.jl")
+include("geom_density.jl")
 include("geom_path.jl")
 include("geom_point.jl")
 include("geom_smooth.jl")
@@ -33,6 +34,7 @@ export @geom_path, @geom_line, @geom_step
 export @geom_violin, @geom_boxplot
 export @geom_contour, @geom_tile
 export @geom_text, @geom_label
+export @geom_density
 export @labs, @lims
 export @scale_x_continuous, @scale_y_continuous
 export @scale_x_log10, @scale_y_log10, @scale_x_log2, @scale_y_log2, @scale_x_log, @scale_y_log  

src/geom_density.jl

@@ -0,0 +1,37 @@
+"""
+    @geom_density(aes(...), ...)
+    
+    Represent data as a smooth density curve. 
+
+    # Arguments
+
+    - `aes(...)`: the names of the columns in the plot DataFrame and their corresponding aesthetic.
+    - `...`: options that are not mapped to a column 
+
+    # Required Aesthetics
+
+    - x
+
+    # Supported Optional Aesthetics
+
+    - alpha
+    - stroke
+    - colour/color
+
+    # Supported Options
+
+    - alpha
+    - stroke
+    - colour/color
+
+"""
+macro geom_density(exprs...)
+    aes_dict, args_dict = extract_aes(:($(exprs)))
+
+    args_dict["geom_name"] = "geom_density"
+
+    return build_geom(aes_dict, args_dict, 
+        ["x"], # required aesthetics
+        nothing, # function for visual layer
+        AlgebraOfGraphics.density()) # function for analysis layer    
+end