From 13e71b9187f0eec123cda3f45b06582da242624b Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Tue, 24 Oct 2017 22:09:56 +0530
Subject: [PATCH 1/7] Adds excelx exporter with axlsx dependency

---
 Gemfile                         |   1 +
 lib/daru/io/exporters/excelx.rb | 110 ++++++++++++++++++++++++++++++++
 2 files changed, 111 insertions(+)
 create mode 100644 lib/daru/io/exporters/excelx.rb

diff --git a/Gemfile b/Gemfile
index 3889d5a..a912ef0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,6 +3,7 @@ gemspec
 
 group :optional do
   gem 'activerecord', '~> 4.0'
+  gem 'axlsx'
   gem 'avro'
   gem 'dbd-sqlite3'
   gem 'dbi'
diff --git a/lib/daru/io/exporters/excelx.rb b/lib/daru/io/exporters/excelx.rb
new file mode 100644
index 0000000..2d097c7
--- /dev/null
+++ b/lib/daru/io/exporters/excelx.rb
@@ -0,0 +1,110 @@
+require 'daru/io/exporters/base'
+
+module Daru
+  module IO
+    module Exporters
+      # Excelx Exporter Class, that extends `to_excelx_string` and `write_excelx` methods to
+      # `Daru::DataFrame` instance variables
+      class Excelx < Base
+        Daru::DataFrame.register_io_module :to_excelx_string, self
+        Daru::DataFrame.register_io_module :write_excelx, self
+
+        # Initializes an Excel Exporter instance.
+        #
+        # @param dataframe [Daru::DataFrame] A dataframe to export. Supports even dataframes
+        #   with multi-index.
+        # @param sheet [String] A sheet name, to export the dataframe into.
+        #
+        # @example Initializing an Excel Exporter instance
+        #   df = Daru::DataFrame.new([[1,2],[3,4]], order: [:a, :b])
+        #
+        #   #=> #<Daru::DataFrame(2x2)>
+        #   #      a   b
+        #   #  0   1   3
+        #   #  1   2   4
+        #
+        #   simple_instance = Daru::IO::Exporters::Excel.new(df)
+        #   formatted_instance = Daru::IO::Exporters::Excel.new(
+        #     df,
+        #     header: { color: :red, weight: :bold },
+        #     index: false,
+        #     data: { color: :blue }
+        #   )
+        def initialize(dataframe, sheet: '0', header: true, data: true, index: true)
+          optional_gem 'axlsx'
+
+          super(dataframe)
+          @data   = data
+          @index  = index
+          @sheet  = sheet
+          @header = header
+        end
+
+        # Exports an Excelx Exporter instance to a file-writable String.
+        #
+        # @return [String] A file-writable string
+        #
+        # @example Getting a file-writable string from Excel Exporter instance
+        #   simple_instance.to_s #! same as df.to_avro_string(schema)
+        #
+        #   #=> "\xD0\xCF\u0011\u0871\u001A\xE1\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000..."
+        def to_s
+          super
+        end
+
+        # Exports an Excelx Exporter instance to an xlsx file.
+        #
+        # @param path [String] Path of excelx file where the dataframe is to be saved
+        #
+        # @example Writing an Excel Exporterx instance to an xlsx file
+        #   instance.write('filename.xlsx')
+        def write(path)
+          @package = Axlsx::Package.new
+          @workbook = @package.workbook
+
+          process_offsets
+
+          @workbook.add_worksheet(:name => @sheet) do |sheet|
+            sheet.add_row(fetch_headers)
+
+            @dataframe.each_row_with_index do |row, idx|
+              sheet.add_row(fetch_index(idx) + fetch_data(row))
+            end
+          end
+
+          @package.serialize(path)
+        end
+
+        private
+
+        def process_offsets
+          @row_offset   = @header ? 1 : 0
+          @col_offset   = 0 unless @index
+          @col_offset ||= @dataframe.index.is_a?(Daru::MultiIndex) ? @dataframe.index.width : 1
+        end
+
+        def fetch_headers
+          fetching([' '] * @col_offset + @dataframe.vectors.map(&:to_s), @header)
+        end
+
+        def fetch_index(idx)
+          fetching(idx, @index)
+        end
+
+        def fetch_data(row)
+          fetching(row, @data)
+        end
+
+        def fetching(idx, format)
+          return [] unless format
+
+          case idx
+          when Daru::Vector then idx.to_a
+          when Array then idx.map(&:to_s)
+          else [idx.to_s]
+          end
+        end
+      end
+    end
+  end
+end

From aafde94dca2fb572386d26c815d7b89c580492c4 Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Tue, 24 Oct 2017 22:48:37 +0530
Subject: [PATCH 2/7] Changes source of axlsx from rubygems to git

---
 Gemfile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Gemfile b/Gemfile
index a912ef0..3c301c3 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,7 +3,6 @@ gemspec
 
 group :optional do
   gem 'activerecord', '~> 4.0'
-  gem 'axlsx'
   gem 'avro'
   gem 'dbd-sqlite3'
   gem 'dbi'
@@ -18,4 +17,5 @@ group :optional do
   gem 'sqlite3'
 end
 
+gem 'axlsx', git: 'https://github.com/randym/axlsx.git'
 gem 'saharspec', git: 'https://github.com/zverok/saharspec.git'

From 1035f6c85a78c36ee4adfd4b6a049eb9fdecc969 Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Wed, 25 Oct 2017 20:37:38 +0530
Subject: [PATCH 3/7] Re-writes excelx exporter with rubyXL gem

---
 Gemfile                         |  2 +-
 lib/daru/io/exporters/base.rb   |  4 ++--
 lib/daru/io/exporters/excelx.rb | 37 +++++++++++++++++++--------------
 lib/daru/io/importers/excel.rb  |  4 ++--
 lib/daru/io/link.rb             |  2 +-
 5 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/Gemfile b/Gemfile
index 3c301c3..cea7dd1 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,10 +12,10 @@ group :optional do
   gem 'redis'
   gem 'roo', '~> 2.7.0'
   gem 'rsruby'
+  gem 'rubyXL'
   gem 'snappy'
   gem 'spreadsheet', '~> 1.1.1'
   gem 'sqlite3'
 end
 
-gem 'axlsx', git: 'https://github.com/randym/axlsx.git'
 gem 'saharspec', git: 'https://github.com/zverok/saharspec.git'
diff --git a/lib/daru/io/exporters/base.rb b/lib/daru/io/exporters/base.rb
index 33ab203..5cafd28 100644
--- a/lib/daru/io/exporters/base.rb
+++ b/lib/daru/io/exporters/base.rb
@@ -41,8 +41,8 @@ def initialize(dataframe)
         #
         #   instance = Daru::IO::Exporters::Format.new(opts)
         #   instance.to_s #! same as df.to_format_string(opts)
-        def to_s
-          tempfile = Tempfile.new('tempfile')
+        def to_s(file_extension: '')
+          tempfile = Tempfile.new(['filename', file_extension])
           path     = tempfile.path
           write(path)
 
diff --git a/lib/daru/io/exporters/excelx.rb b/lib/daru/io/exporters/excelx.rb
index 2d097c7..b07302f 100644
--- a/lib/daru/io/exporters/excelx.rb
+++ b/lib/daru/io/exporters/excelx.rb
@@ -30,8 +30,8 @@ class Excelx < Base
         #     index: false,
         #     data: { color: :blue }
         #   )
-        def initialize(dataframe, sheet: '0', header: true, data: true, index: true)
-          optional_gem 'axlsx'
+        def initialize(dataframe, sheet: 'Sheet0', header: true, data: true, index: true)
+          optional_gem 'rubyXL'
 
           super(dataframe)
           @data   = data
@@ -49,7 +49,7 @@ def initialize(dataframe, sheet: '0', header: true, data: true, index: true)
         #
         #   #=> "\xD0\xCF\u0011\u0871\u001A\xE1\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000..."
         def to_s
-          super
+          super(file_extension: '.xlsx')
         end
 
         # Exports an Excelx Exporter instance to an xlsx file.
@@ -59,20 +59,18 @@ def to_s
         # @example Writing an Excel Exporterx instance to an xlsx file
         #   instance.write('filename.xlsx')
         def write(path)
-          @package = Axlsx::Package.new
-          @workbook = @package.workbook
-
+          @workbook = RubyXL::Workbook.new
+          @sheet    = @workbook.add_worksheet(@sheet)
           process_offsets
 
-          @workbook.add_worksheet(:name => @sheet) do |sheet|
-            sheet.add_row(fetch_headers)
+          write_row(@header ? 0 : 1, fetch_headers)
 
-            @dataframe.each_row_with_index do |row, idx|
-              sheet.add_row(fetch_index(idx) + fetch_data(row))
-            end
+          @dataframe.each_row_with_index.with_index do |(row, idx), i|
+            write_row(@row_offset+i, fetch_index(idx) + fetch_data(row))
           end
 
-          @package.serialize(path)
+          @workbook.write(path)
+          true
         end
 
         private
@@ -84,26 +82,33 @@ def process_offsets
         end
 
         def fetch_headers
-          fetching([' '] * @col_offset + @dataframe.vectors.map(&:to_s), @header)
+          formatting([' '] * @col_offset + @dataframe.vectors.map(&:to_s), @header)
         end
 
         def fetch_index(idx)
-          fetching(idx, @index)
+          formatting(idx, @index)
         end
 
         def fetch_data(row)
-          fetching(row, @data)
+          formatting(row, @data)
         end
 
-        def fetching(idx, format)
+        def formatting(idx, format)
           return [] unless format
 
           case idx
           when Daru::Vector then idx.to_a
           when Array then idx.map(&:to_s)
+          when Daru::MultiIndex then idx
           else [idx.to_s]
           end
         end
+
+        def write_row(row_index, row_array)
+          row_array.each_with_index do |element, col_index|
+            @sheet.insert_cell(row_index, col_index, element.to_s)
+          end
+        end
       end
     end
   end
diff --git a/lib/daru/io/importers/excel.rb b/lib/daru/io/importers/excel.rb
index e5bf2ff..7465541 100644
--- a/lib/daru/io/importers/excel.rb
+++ b/lib/daru/io/importers/excel.rb
@@ -10,9 +10,9 @@ class Excel < Base
         Daru::DataFrame.register_io_module :read_excel do |*args, &io_block|
           if args.first.end_with?('.xlsx')
             require 'daru/io/importers/excelx'
-            Daru::IO::Importers::Excelx.new(*args[1..-1], &io_block).read(*args[0])
+            Daru::IO::Importers::Excelx.new.read(*args[0]).call(*args[1..-1], &io_block)
           else
-            Daru::IO::Importers::Excel.new(*args[1..-1], &io_block).read(*args[0])
+            Daru::IO::Importers::Excel.new.read(*args[0]).call(*args[1..-1], &io_block)
           end
         end
 
diff --git a/lib/daru/io/link.rb b/lib/daru/io/link.rb
index 7e44aa4..7d3b391 100644
--- a/lib/daru/io/link.rb
+++ b/lib/daru/io/link.rb
@@ -62,7 +62,7 @@ def register_exporter(function, instance)
           case function.to_s
           when /\Ato_.*_string\Z/ then instance.new(self, *args, &io_block).to_s
           when /\Ato_/            then instance.new(self, *args, &io_block).to
-          when /Awrite_/          then instance.new(self, *args[1..-1], &io_block).write(*args[0])
+          when /\Awrite_/          then instance.new(self, *args[1..-1], &io_block).write(*args[0])
           end
         end
       end

From 01fc93f1dc43bd6a207093e5b1d77cade3ec37ed Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Wed, 25 Oct 2017 20:58:03 +0530
Subject: [PATCH 4/7] Updates YARD Doc for Excelx Exporter

---
 lib/daru/io/exporters/avro.rb   |  1 +
 lib/daru/io/exporters/csv.rb    |  1 +
 lib/daru/io/exporters/excel.rb  |  3 ++-
 lib/daru/io/exporters/excelx.rb | 31 +++++++++++++++----------------
 lib/daru/io/exporters/json.rb   |  1 +
 lib/daru/io/exporters/r_data.rb |  1 +
 lib/daru/io/exporters/rds.rb    |  1 +
 lib/daru/io/link.rb             | 32 +++++++++++++++++---------------
 8 files changed, 39 insertions(+), 32 deletions(-)

diff --git a/lib/daru/io/exporters/avro.rb b/lib/daru/io/exporters/avro.rb
index ed0ca7f..d7ae874 100644
--- a/lib/daru/io/exporters/avro.rb
+++ b/lib/daru/io/exporters/avro.rb
@@ -78,6 +78,7 @@ def write(path)
           @writer.close
 
           File.open(path, 'w') { |file| file.write(@buffer.string) }
+          true
         end
 
         private
diff --git a/lib/daru/io/exporters/csv.rb b/lib/daru/io/exporters/csv.rb
index 3227ff1..897fc77 100644
--- a/lib/daru/io/exporters/csv.rb
+++ b/lib/daru/io/exporters/csv.rb
@@ -80,6 +80,7 @@ def write(path)
             contents.each { |content| csv << content }
             csv.close
           end
+          true
         end
 
         private
diff --git a/lib/daru/io/exporters/excel.rb b/lib/daru/io/exporters/excel.rb
index bc7662e..bc2c742 100755
--- a/lib/daru/io/exporters/excel.rb
+++ b/lib/daru/io/exporters/excel.rb
@@ -62,7 +62,7 @@ def initialize(dataframe, header: true, data: true, index: true)
         # @return [String] A file-writable string
         #
         # @example Getting a file-writable string from Excel Exporter instance
-        #   simple_instance.to_s #! same as df.to_avro_string(schema)
+        #   simple_instance.to_s
         #
         #   #=> "\xD0\xCF\u0011\u0871\u001A\xE1\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000..."
         #
@@ -92,6 +92,7 @@ def write(path)
           end
 
           @book.write(path)
+          true
         end
 
         private
diff --git a/lib/daru/io/exporters/excelx.rb b/lib/daru/io/exporters/excelx.rb
index b07302f..d0b088e 100644
--- a/lib/daru/io/exporters/excelx.rb
+++ b/lib/daru/io/exporters/excelx.rb
@@ -9,11 +9,18 @@ class Excelx < Base
         Daru::DataFrame.register_io_module :to_excelx_string, self
         Daru::DataFrame.register_io_module :write_excelx, self
 
-        # Initializes an Excel Exporter instance.
+        # Initializes an Excelx Exporter instance.
         #
         # @param dataframe [Daru::DataFrame] A dataframe to export. Supports even dataframes
         #   with multi-index.
-        # @param sheet [String] A sheet name, to export the dataframe into.
+        # @param sheet [String] A sheet name, to export the dataframe into. Defaults to
+        #   'Sheet0'.
+        # @param header [Boolean] Defaults to true. When set to false or nil,
+        #   headers are not written.
+        # @param data [Boolean] Defaults to true. When set to false or nil,
+        #   data values are not written.
+        # @param index [Boolean] Defaults to true. When set to false or nil,
+        #   index values are not written
         #
         # @example Initializing an Excel Exporter instance
         #   df = Daru::DataFrame.new([[1,2],[3,4]], order: [:a, :b])
@@ -23,13 +30,7 @@ class Excelx < Base
         #   #  0   1   3
         #   #  1   2   4
         #
-        #   simple_instance = Daru::IO::Exporters::Excel.new(df)
-        #   formatted_instance = Daru::IO::Exporters::Excel.new(
-        #     df,
-        #     header: { color: :red, weight: :bold },
-        #     index: false,
-        #     data: { color: :blue }
-        #   )
+        #   instance = Daru::IO::Exporters::Excelx.new(df)
         def initialize(dataframe, sheet: 'Sheet0', header: true, data: true, index: true)
           optional_gem 'rubyXL'
 
@@ -44,10 +45,10 @@ def initialize(dataframe, sheet: 'Sheet0', header: true, data: true, index: true
         #
         # @return [String] A file-writable string
         #
-        # @example Getting a file-writable string from Excel Exporter instance
-        #   simple_instance.to_s #! same as df.to_avro_string(schema)
+        # @example Getting a file-writable string from Excelx Exporter instance
+        #   instance.to_s
         #
-        #   #=> "\xD0\xCF\u0011\u0871\u001A\xE1\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000..."
+        #   #=> "PK\u0003\u0004\u0014\u0000\u0000\u0000\b\u0000X\xA5YK\u0018\x87\xFC\u0017..."
         def to_s
           super(file_extension: '.xlsx')
         end
@@ -56,7 +57,7 @@ def to_s
         #
         # @param path [String] Path of excelx file where the dataframe is to be saved
         #
-        # @example Writing an Excel Exporterx instance to an xlsx file
+        # @example Writing an Excelx Exporter instance to an xlsx file
         #   instance.write('filename.xlsx')
         def write(path)
           @workbook = RubyXL::Workbook.new
@@ -97,9 +98,7 @@ def formatting(idx, format)
           return [] unless format
 
           case idx
-          when Daru::Vector then idx.to_a
-          when Array then idx.map(&:to_s)
-          when Daru::MultiIndex then idx
+          when Daru::Vector, Daru::MultiIndex, Array then idx.map(&:to_s)
           else [idx.to_s]
           end
         end
diff --git a/lib/daru/io/exporters/json.rb b/lib/daru/io/exporters/json.rb
index 1832f5a..5454be9 100644
--- a/lib/daru/io/exporters/json.rb
+++ b/lib/daru/io/exporters/json.rb
@@ -487,6 +487,7 @@ def write(path)
           File.open(path, 'w') do |file|
             file.write(::JSON.send(@pretty ? :pretty_generate : :generate, to))
           end
+          true
         end
 
         private
diff --git a/lib/daru/io/exporters/r_data.rb b/lib/daru/io/exporters/r_data.rb
index f9d3eec..434a28f 100644
--- a/lib/daru/io/exporters/r_data.rb
+++ b/lib/daru/io/exporters/r_data.rb
@@ -59,6 +59,7 @@ def write(path)
           end.flatten
           @statements << "save(#{@options.keys.map(&:to_s).join(', ')}, file='#{path}')"
           @statements.each { |statement| @instance.eval_R(statement) }
+          true
         end
       end
     end
diff --git a/lib/daru/io/exporters/rds.rb b/lib/daru/io/exporters/rds.rb
index f744b16..faa08b8 100644
--- a/lib/daru/io/exporters/rds.rb
+++ b/lib/daru/io/exporters/rds.rb
@@ -53,6 +53,7 @@ def write(path)
           @statements  = process_statements(@r_variable, @dataframe)
           @statements << "saveRDS(#{@r_variable}, file='#{path}')"
           @statements.each { |statement| @instance.eval_R(statement) }
+          true
         end
 
         private
diff --git a/lib/daru/io/link.rb b/lib/daru/io/link.rb
index 7d3b391..63239f3 100644
--- a/lib/daru/io/link.rb
+++ b/lib/daru/io/link.rb
@@ -25,20 +25,22 @@ class << self
       #
       # #### Exporters
       #
-      # | `Daru::DataFrame` instance method | `Daru::IO::Exporters` class        |
-      # | --------------------------------- | -----------------------------------|
-      # | `Daru::DataFrame.to_avro_string`  | {Daru::IO::Exporters::Avro#to_s}   |
-      # | `Daru::DataFrame.write_avro`      | {Daru::IO::Exporters::Avro#write}  |
-      # | `Daru::DataFrame.to_csv_string`   | {Daru::IO::Exporters::CSV#to_s}    |
-      # | `Daru::DataFrame.write_csv`       | {Daru::IO::Exporters::CSV#write}   |
-      # | `Daru::DataFrame.to_excel_string` | {Daru::IO::Exporters::Excel#to_s}  |
-      # | `Daru::DataFrame.write_excel`     | {Daru::IO::Exporters::Excel#write} |
-      # | `Daru::DataFrame.to_json`         | {Daru::IO::Exporters::JSON#to}     |
-      # | `Daru::DataFrame.to_json_string`  | {Daru::IO::Exporters::JSON#to_s}   |
-      # | `Daru::DataFrame.write_json`      | {Daru::IO::Exporters::JSON#write}  |
-      # | `Daru::DataFrame.to_rds_string`   | {Daru::IO::Exporters::RDS#to_s}    |
-      # | `Daru::DataFrame.write_rds`       | {Daru::IO::Exporters::RDS#write}   |
-      # | `Daru::DataFrame.to_sql`          | {Daru::IO::Exporters::SQL#to}      |
+      # | `Daru::DataFrame` instance method  | `Daru::IO::Exporters` class         |
+      # | -----------------------------------| ------------------------------------|
+      # | `Daru::DataFrame.to_avro_string`   | {Daru::IO::Exporters::Avro#to_s}    |
+      # | `Daru::DataFrame.write_avro`       | {Daru::IO::Exporters::Avro#write}   |
+      # | `Daru::DataFrame.to_csv_string`    | {Daru::IO::Exporters::CSV#to_s}     |
+      # | `Daru::DataFrame.write_csv`        | {Daru::IO::Exporters::CSV#write}    |
+      # | `Daru::DataFrame.to_excel_string`  | {Daru::IO::Exporters::Excel#to_s}   |
+      # | `Daru::DataFrame.write_excel`      | {Daru::IO::Exporters::Excel#write}  |
+      # | `Daru::DataFrame.to_excelx_string` | {Daru::IO::Exporters::Excelx#to_s}  |
+      # | `Daru::DataFrame.write_excelx`     | {Daru::IO::Exporters::Excelx#write} |
+      # | `Daru::DataFrame.to_json`          | {Daru::IO::Exporters::JSON#to}      |
+      # | `Daru::DataFrame.to_json_string`   | {Daru::IO::Exporters::JSON#to_s}    |
+      # | `Daru::DataFrame.write_json`       | {Daru::IO::Exporters::JSON#write}   |
+      # | `Daru::DataFrame.to_rds_string`    | {Daru::IO::Exporters::RDS#to_s}     |
+      # | `Daru::DataFrame.write_rds`        | {Daru::IO::Exporters::RDS#write}    |
+      # | `Daru::DataFrame.to_sql`           | {Daru::IO::Exporters::SQL#to}       |
       #
       # @param function [Symbol] Functon name to be monkey-patched into +Daru::DataFrame+
       # @param instance [Class] The Daru-IO class to be linked to monkey-patched function
@@ -62,7 +64,7 @@ def register_exporter(function, instance)
           case function.to_s
           when /\Ato_.*_string\Z/ then instance.new(self, *args, &io_block).to_s
           when /\Ato_/            then instance.new(self, *args, &io_block).to
-          when /\Awrite_/          then instance.new(self, *args[1..-1], &io_block).write(*args[0])
+          when /\Awrite_/         then instance.new(self, *args[1..-1], &io_block).write(*args[0])
           end
         end
       end

From a6746c45d8cea64f6e5c4b036cf2e2d6cb64d0ea Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Wed, 25 Oct 2017 21:42:08 +0530
Subject: [PATCH 5/7] Updates README with Excelx Exporter

---
 CONTRIBUTING.md |  2 +-
 README.md       | 24 +++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ccfee3f..10c0a20 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -39,7 +39,7 @@ Please proceed with a Pull Request only after you're assigned. It'd be sad if yo
 
 4. Add any gem dependencies required for the Format Importer to the `:optional` group of the Gemfile.
 
-5. Add code and YARD documentation to `lib/daru/io/importers/format.rb`, consistent with other IO modules.
+5. Add code and YARD documentation to `lib/daru/io/importers/format.rb`, consistent with other IO modules. Update the `README.md` if required.
 
 6. Add tests to `spec/daru/io/importers/format_spec.rb`. Add any `.format` files required for importer in `spec/fixtures/format/` directory.
 
diff --git a/README.md b/README.md
index 132a4c2..e77c667 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ While supporting various IO modules, daru-io also provides an easier way of addi
 
 - [Installation](#installation)
 - *[Importers](#importers): [ActiveRecord](#activerecord-importer), [Avro](#avro-importer), [CSV](#csv-importer), [Excel](#excel-importer), [Excelx](#excelx-importer), [HTML](#html-importer), [JSON](#json-importer), [Mongo](#mongo-importer), [Plaintext](#plaintext-importer), [RData](#rdata-importer), [RDS](#rds-importer), [Redis](#redis-importer), [SQL](#sql-importer)*
-- *[Exporters](#exporters): [Avro](#avro-exporter), [CSV](#csv-exporter), [Excel](#excel-exporter), [JSON](#json-exporter), [RData](#rdata-exporter), [RDS](#rds-exporter), [SQL](#sql-exporter)*
+- *[Exporters](#exporters): [Avro](#avro-exporter), [CSV](#csv-exporter), [Excel](#excel-exporter), [Excelx](#excelx-exporter), [JSON](#json-exporter), [RData](#rdata-exporter), [RDS](#rds-exporter), [SQL](#sql-exporter)*
 - [Creating your own IO modules](#creating-your-own-io-modules)
 - [Contributing](#contributing)
 - [License](#license)
@@ -458,6 +458,28 @@ Exports a **Daru::DataFrame** into a **.xls** file.
     df.write_excel('path/to/file.xls', header: {color: :red, weight: :bold}, data: {color: :blue }, index: false)
     ```
 
+### Excelx Exporter
+
+[(Go to Table of Contents)](#table-of-contents)
+
+Exports a **Daru::DataFrame** into a **.xlsx** file.
+
+- **Docs**: [rubydoc.info](http://www.rubydoc.info/github/athityakumar/daru-io/master/Daru/IO/Exporters/Excelx)
+- **Gem Dependencies**: `rubyXL` gem
+- **Usage**:
+    ```ruby
+    #! Partially require just Excelx Exporter
+    require 'daru/io/exporters/excelx'
+
+    #! Usage from Daru::IO
+    string = Daru::IO::Exporters::Excelx.new(df, index: false).to_s
+    Daru::IO::Exporters::Excelx.new(df, index: false).write('path/to/file.xlsx')
+
+    #! Usage from Daru::DataFrame
+    string = df.to_excelx_string(index: false)
+    df.write_excel('path/to/file.xlsx', index: false)
+    ```
+
 ### JSON Exporter
 
 [(Go to Table of Contents)](#table-of-contents)

From f4784705f0c72b67b6d3e406342b06ba802e3879 Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Thu, 26 Oct 2017 02:11:11 +0530
Subject: [PATCH 6/7] Adds tests for Excelx Exporter

---
 spec/daru/io/exporters/csv_spec.rb    |  2 +-
 spec/daru/io/exporters/excel_spec.rb  |  2 +-
 spec/daru/io/exporters/excelx_spec.rb | 39 +++++++++++++++++++++++++++
 spec/spec_helper.rb                   |  1 +
 4 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 spec/daru/io/exporters/excelx_spec.rb

diff --git a/spec/daru/io/exporters/csv_spec.rb b/spec/daru/io/exporters/csv_spec.rb
index e3dad6b..1a78da4 100644
--- a/spec/daru/io/exporters/csv_spec.rb
+++ b/spec/daru/io/exporters/csv_spec.rb
@@ -8,7 +8,7 @@
   before { described_class.new(df, opts).write(tempfile.path) }
 
   context 'writes DataFrame to a CSV file' do
-    subject { Daru::DataFrame.rows content[1..-1].map { |x| x.map { |y| convert(y) } }, order: content[0] }
+    subject { Daru::DataFrame.rows(content[1..-1].map { |x| x.map { |y| convert(y) } }, order: content[0]) }
 
     let(:opts) { {} }
     let(:content) { CSV.read(tempfile.path) }
diff --git a/spec/daru/io/exporters/excel_spec.rb b/spec/daru/io/exporters/excel_spec.rb
index eacc037..0944101 100644
--- a/spec/daru/io/exporters/excel_spec.rb
+++ b/spec/daru/io/exporters/excel_spec.rb
@@ -2,7 +2,7 @@
   include_context 'exporter setup'
 
   let(:filename) { 'test_write.xls' }
-  let(:content)  { Spreadsheet.open tempfile.path }
+  let(:content)  { Spreadsheet.open(tempfile.path) }
   let(:opts)     { {header: {color: :blue}, data: {color: :red}, index: {color: :green}} }
 
   before { described_class.new(df, **opts).write(tempfile.path) }
diff --git a/spec/daru/io/exporters/excelx_spec.rb b/spec/daru/io/exporters/excelx_spec.rb
new file mode 100644
index 0000000..c554c5e
--- /dev/null
+++ b/spec/daru/io/exporters/excelx_spec.rb
@@ -0,0 +1,39 @@
+RSpec.describe Daru::IO::Exporters::Excelx do
+  include_context 'exporter setup'
+
+  let(:filename) { ['test_write', '.xlsx'] }
+  let(:content)  { Roo::Excelx.new(tempfile.path).sheet('Sheet0').to_a }
+
+  before { described_class.new(df, **opts).write(tempfile.path) }
+
+  context 'writes to excelx worksheet without index' do
+    subject { Daru::DataFrame.rows(content[1..-1].map { |x| x.map { |y| convert(y) } }, order: content[0]) }
+
+    let(:opts) { {index: false} }
+
+    it_behaves_like 'exact daru dataframe',
+      ncols: 4,
+      nrows: 5,
+      order: %w[a b c d],
+      data: [
+        [1,2,3,4,5],
+        [11,22,33,44,55],
+        ['a', 'g', 4, 5,'addadf'],
+        ['', 23, 4,'a','ff']
+      ]
+  end
+
+  context 'writes to excelx worksheet with multi-index' do
+    subject { content.map { |x| x.map { |y| convert(y) } } }
+
+    let(:df) do
+      Daru::DataFrame.new(
+        [[1,2],[3,4]],
+        order: %i[x y],
+        index: [%i[a b c], %i[d e f]]
+      )
+    end
+
+    it { is_expected.to eq([[' ', ' ', ' ', 'x', 'y'], ['a', 'b', 'c', 1, 3], ['d', 'e', 'f', 2, 4]]) }
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index c5b5745..6775045 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -17,6 +17,7 @@
 require 'dbd/SQLite3'
 require 'active_record'
 require 'redis'
+require 'roo'
 require 'dbi'
 require 'jsonpath'
 require 'nokogiri'

From 2f2bd6b62e4efef5f26e297a54c26764395f3c59 Mon Sep 17 00:00:00 2001
From: Athitya <athityakumar@gmail.com>
Date: Thu, 26 Oct 2017 02:30:31 +0530
Subject: [PATCH 7/7] Fixes minor rubocop offense

---
 daru-io.gemspec | 1 +
 1 file changed, 1 insertion(+)

diff --git a/daru-io.gemspec b/daru-io.gemspec
index ff5f4ab..f4c5c9e 100644
--- a/daru-io.gemspec
+++ b/daru-io.gemspec
@@ -33,5 +33,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'simplecov'
   spec.add_development_dependency 'webmock'
   spec.add_development_dependency 'yard'
+
   spec.add_development_dependency 'guard-rspec' if RUBY_VERSION >= '2.2.5'
 end