Fix os operator

SimoxUtility/math/regression/linear3d.cpp

@@ -76,9 +76,10 @@ simox::math::operator<<(std::ostream& os, const LinearRegression3D& r)
         {
             os << ", ";
         }
-        os << r.coefficients(row, 0)
-           << " + " << r.coefficients(row, 1) << " * x_" << row
-           << " = y_" << row;
+        os << "y_" << row
+           << " = " << r.coefficients(row, 0)
+           << " + " << r.coefficients(row, 1) << " * x"
+              ;
     }
     os << " ]";
     return os;

SimoxUtility/math/regression/linear3d.h

@@ -7,8 +7,8 @@ namespace simox::math
 {
 
     /**
-     * @brief A linear regression model of the form a + b * x = y,
-     * or per dimension, a_i + b_i * x = y_i.
+     * @brief A linear regression model of the form y = a + b * x,
+     * or per dimension, y_i = a_i + b_i * x.
      *
      * - x is the scalar input variable (e.g. time)
      * - y is 3D vector output variable (e.g. position)

SimoxUtility/tests/math/regression/linear3d.cpp

@@ -86,8 +86,6 @@ BOOST_AUTO_TEST_CASE(test_linear_regression_3d_fit_and_predict_with_input_offset
 
     // Coefficients are different now, but prediction should be the same.
 
-    // Predict
-
     BOOST_CHECK_LE((regression.predict(xs[0]) - ys[0]).norm(), prec);
     BOOST_CHECK_LE((regression.predict(xs[1]) - ys[1]).norm(), prec);
     BOOST_CHECK_LE((regression.predict(xs[2]) - ys[2]).norm(), prec);