diff --git a/ext/alglib/alglib.cpp b/ext/alglib/alglib.cpp
index b764ab1..991cfde 100644
--- a/ext/alglib/alglib.cpp
+++ b/ext/alglib/alglib.cpp
@@ -4,8 +4,8 @@
 // #include "numo.hpp"
 #include "dataanalysis.h"
 #include "statistics.h"
-#include "alglib_array_converters.hpp"
-#include "alglib_utils.hpp"
+#include "alglib_array_converters.h"
+#include "alglib_utils.h"
 
 using namespace Rice;
 
diff --git a/ext/alglib/alglib_array_converters.cpp b/ext/alglib/alglib_array_converters.cpp
new file mode 100644
index 0000000..0f186f1
--- /dev/null
+++ b/ext/alglib/alglib_array_converters.cpp
@@ -0,0 +1,81 @@
+
+#include "alglib_array_converters.h"
+
+// Convert Ruby Array to real_1d_array
+alglib::real_1d_array ruby_array_to_real_1d_array(Array ruby_array)
+{
+    alglib::real_1d_array real_array;
+    real_array.setlength(ruby_array.size());
+    std::transform(ruby_array.begin(), ruby_array.end(), real_array.getcontent(), [](const Object &o)
+                   { return detail::From_Ruby<double>().convert(o.value()); });
+    return real_array;
+}
+
+// Convert Ruby Array to integer_1d_array
+alglib::integer_1d_array ruby_array_to_integer_1d_array(Array ruby_array)
+{
+    alglib::integer_1d_array integer_array;
+    integer_array.setlength(ruby_array.size());
+    std::transform(ruby_array.begin(), ruby_array.end(), integer_array.getcontent(), [](const Object &o)
+                   { return detail::From_Ruby<int>().convert(o.value()); });
+    return integer_array;
+}
+
+/*
+Below functions are experimental implementations.
+Do not expect this to work!
+*/
+
+// Convert Ruby 2d Array to real_2d_array
+alglib::real_2d_array ruby_array_to_real_2d_array(Array ruby_array, int &rows, int &cols)
+{
+    alglib::real_2d_array real_array;
+    rows = ruby_array.size();
+    cols = detail::From_Ruby<Array>().convert(ruby_array.call("first")).size();
+    // debug
+    real_array.setlength(rows, cols);
+
+    Array::iterator it = ruby_array.begin();
+    Array::iterator end = ruby_array.end();
+
+    for (int i = 0; it != end; ++it, ++i)
+    {
+        Array row = detail::From_Ruby<Array>().convert(it->value());
+        // check if all rows have the same size
+        if (row.size() != cols)
+        {
+            throw std::invalid_argument("All rows must have the same size");
+        }
+
+        std::transform(row.begin(), row.end(), real_array[i], [](const Object &o)
+                       { return detail::From_Ruby<double>().convert(o.value()); });
+    }
+    return real_array;
+}
+
+// Convert real_1d_array to Ruby Array
+Array real_1d_array_to_ruby_array(alglib::real_1d_array real_array)
+{
+    Array result;
+    for (int i = 0; i < real_array.length(); i++)
+    {
+        result.push(real_array[i]);
+    }
+    return result;
+}
+
+// Convert real_2d_array to Ruby Array
+Array real_2d_array_to_ruby_array(alglib::real_2d_array real_array)
+{
+    Array result;
+    for (int i = 0; i < real_array.rows(); i++)
+    {
+        Array row;
+        for (int j = 0; j < real_array.cols(); j++)
+        {
+            row.push(real_array[i][j]);
+        }
+        result.push(row);
+    }
+    return result;
+}
\ No newline at end of file
diff --git a/ext/alglib/alglib_array_converters.hpp b/ext/alglib/alglib_array_converters.hpp
deleted file mode 100644
index a9b4371..0000000
--- a/ext/alglib/alglib_array_converters.hpp
+++ /dev/null
@@ -1,14 +0,0 @@
-#include <rice/rice.hpp>
-#include <rice/stl.hpp>
-#include "ap.h"
-
-using namespace Rice;
-
-alglib::real_1d_array ruby_array_to_real_1d_array(Array ruby_array);
-
-// Experimental implementations - do not expect this to work!
-
-alglib::integer_1d_array ruby_array_to_integer_1d_array(Array ruby_array);
-alglib::real_2d_array ruby_array_to_real_2d_array(Array ruby_array, int &rows, int &cols);
-Array real_1d_array_to_ruby_array(alglib::real_1d_array real_array);
-Array real_2d_array_to_ruby_array(alglib::real_2d_array real_array);
diff --git a/ext/alglib/alglib_utils.cpp b/ext/alglib/alglib_utils.cpp
index 0ed825c..32e313d 100644
--- a/ext/alglib/alglib_utils.cpp
+++ b/ext/alglib/alglib_utils.cpp
@@ -1,4 +1,4 @@
-#include "alglib_utils.hpp"
+#include "alglib_utils.h"
 
 // Check if two arrays are the same size
 void check_size(Array x, Array y)
diff --git a/ext/alglib/alglib_utils.hpp b/ext/alglib/alglib_utils.hpp
deleted file mode 100644
index b974c0e..0000000
--- a/ext/alglib/alglib_utils.hpp
+++ /dev/null
@@ -1,6 +0,0 @@
-#include <rice/rice.hpp>
-#include <rice/stl.hpp>
-
-using namespace Rice;
-
-void check_size(Array x, Array y);
\ No newline at end of file
diff --git a/test/dataanalysis_test.rb b/test/dataanalysis_test.rb
index 579c554..123cef1 100644
--- a/test/dataanalysis_test.rb
+++ b/test/dataanalysis_test.rb
@@ -18,6 +18,15 @@ def test_sample_mean
       v_r <- pca$rotation
       sort(abs(as.vector(v_r)), decreasing = TRUE)[1:6]
     R
+
+    # Why [1:6]?
+    # Because otherwise, the results would span multiple lines.
+    # [1] 0.8164966 0.7071068 0.7071068 0.5773503 0.5773503 0.5773503 0.4082483
+    # [8] 0.4082483 0.0000000
+
+    # Why take the absolute value and sort?
+    # Because the direction of eigenvectors is arbitrary.
+
     expected_v_sort5 = v_sort5.split.map(&:to_f)
 
     result = Alglib.pca_build_basis(
@@ -31,8 +40,6 @@ def test_sample_mean
     assert_in_delta expected_s2[1], result['s2'][1], DELTA
     assert_in_delta expected_s2[2], result['s2'][2], DELTA
 
-    p expected_v_sort5
-    p actual_v_sort5 = result['v'].flatten.map(&:abs).sort.reverse[0..5]
     assert_in_delta expected_v_sort5[0], actual_v_sort5[0], DELTA
     assert_in_delta expected_v_sort5[1], actual_v_sort5[1], DELTA
     assert_in_delta expected_v_sort5[2], actual_v_sort5[2], DELTA