added functionality for creating master index CSV

src/main_index.jl

@@ -0,0 +1,34 @@
+using CSV
+using DataFrames
+
+
+"""
+Create main index TSV file by combining all metadata files
+
+Parameters
+----------
+metadata_folder::String
+    - Folder where metadata TSVs are stored
+master_file::String
+    - TSV file name for combined metadata
+
+Returns
+----------
+nothing
+"""
+function create_master_index(metadata_folder="../metadata/"::String, 
+                            master_file="../metadata/master_idx.tsv"::String)
+
+    # Import all csv files into a dataframe
+    metadata_files = [i for i in readdir(metadata_folder; join=true) if i!=master_file]
+    df = reduce(vcat, [DataFrame(CSV.File(i, delim="|")) for i in metadata_files])
+
+    # remove duplicates
+    df = df[findall(nonunique(df)), :]
+
+    # export df
+    CSV.write(master_file, df, delim="|")
+
+    return
+
+end