To optimize the result in from_excel (#516)

* To optimize the result in from_excel

There are some files have a merged cell in row 1, so the old codes only return the first column.
I put the fixed '0' to opts to custom the row I want.

* daru from_excel

* break up from_excel

* remove needless line

* fix break up

* fix break up

* add testcases

* add testcases

lib/daru/io/io.rb

@@ -39,16 +39,12 @@ class << self
       # Functions for loading/writing Excel files.
 
       def from_excel path, opts={}
-        optional_gem 'spreadsheet', '~>1.1.1'
         opts = {
-          worksheet_id: 0
+          worksheet_id: 0,
+          row_id: 0
         }.merge opts
 
-        worksheet_id = opts[:worksheet_id]
-        book         = Spreadsheet.open path
-        worksheet    = book.worksheet worksheet_id
-        headers      = ArrayHelper.recode_repeated(worksheet.row(0)).map(&:to_sym)
-
+        worksheet, headers = read_from_excel(path, opts)
         df = Daru::DataFrame.new({})
         headers.each_with_index do |h,i|
           col = worksheet.column(i).to_a
@@ -59,6 +55,18 @@ def from_excel path, opts={}
         df
       end
 
+      def read_from_excel path, opts
+        optional_gem 'spreadsheet', '~>1.1.1'
+
+        worksheet_id = opts[:worksheet_id]
+        row_id       = opts[:row_id]
+        book         = Spreadsheet.open path
+        worksheet    = book.worksheet worksheet_id
+        headers      = ArrayHelper.recode_repeated(worksheet.row(row_id)).map(&:to_sym)
+
+        [worksheet, headers]
+      end
+
       def dataframe_write_excel dataframe, path, _opts={}
         book   = Spreadsheet::Workbook.new
         sheet  = book.create_worksheet

spec/io/io_spec.rb

@@ -122,6 +122,38 @@
       end
     end
 
+    context "#from_excel with row_id" do
+      before do
+        id   = Daru::Vector.new(['id', 1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
+        name = Daru::Vector.new(%w(name Alex Claude Peter Franz George Fernand))
+        age  = Daru::Vector.new(['age', 20.0, 23.0, 25.0, nil, 5.5, nil])
+        city = Daru::Vector.new(['city', 'New York', 'London', 'London', 'Paris', 'Tome', nil])
+        a1   = Daru::Vector.new(['a1', 'a,b', 'b,c', 'a', nil, 'a,b,c', nil])
+        @expected_1 = Daru::DataFrame.new({:id2 => id, :name2 => name, :age2 => age}, order: [:id2, :name2, :age2])
+        @expected_2 = Daru::DataFrame.new({
+          :id => id, :name => name, :age => age, :city => city, :a1 => a1
+          }, order: [:id, :name, :age, :city, :a1])
+      end
+
+      it "loads DataFrame from test_xls_2.xls" do
+        df = Daru::DataFrame.from_excel 'spec/fixtures/test_xls_2.xls'
+
+        expect(df.nrows).to eq(7)
+        expect(df.vectors.to_a).to eq([:id2, :name2, :age2])
+        expect(df[:age2][6]).to eq(nil)
+        expect(@expected_1).to eq(df)
+      end
+
+      it "loads DataFrame from test_xls_2.xls with row_id" do
+        df = Daru::DataFrame.from_excel 'spec/fixtures/test_xls_2.xls', {row_id: 1}
+
+        expect(df.nrows).to eq(7)
+        expect(df.vectors.to_a).to eq([:id, :name, :age, :city, :a1])
+        expect(df[:age][6]).to eq(nil)
+        expect(@expected_2).to eq(df)
+      end
+    end
+
     context "#write_excel" do
       before do
         a   = Daru::Vector.new(100.times.map { rand(100) })