diff --git a/Eigen/src/Core/CwiseNullaryOp.h b/Eigen/src/Core/CwiseNullaryOp.h
index 144608ec2..b1923da0f 100644
--- a/Eigen/src/Core/CwiseNullaryOp.h
+++ b/Eigen/src/Core/CwiseNullaryOp.h
@@ -861,6 +861,42 @@ template<typename Derived>
 EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const typename MatrixBase<Derived>::BasisReturnType MatrixBase<Derived>::UnitW()
 { return Derived::Unit(3); }
 
+/** \brief Set the coefficients of \c *this to the i-th unit (basis) vector
+  *
+  * \param i index of the unique coefficient to be set to 1
+  *
+  * \only_for_vectors
+  *
+  * \sa MatrixBase::setIdentity(), class CwiseNullaryOp, MatrixBase::Unit(Index,Index)
+  */
+template<typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Derived& MatrixBase<Derived>::setUnit(Index i)
+{
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
+  eigen_assert(i<size());
+  derived().setZero();
+  derived().coeffRef(i) = Scalar(1);
+  return derived();
+}
+
+/** \brief Resizes to the given \a newSize, and writes the i-th unit (basis) vector into *this.
+  *
+  * \param newSize the new size of the vector
+  * \param i index of the unique coefficient to be set to 1
+  *
+  * \only_for_vectors
+  *
+  * \sa MatrixBase::setIdentity(), class CwiseNullaryOp, MatrixBase::Unit(Index,Index)
+  */
+template<typename Derived>
+EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Derived& MatrixBase<Derived>::setUnit(Index newSize, Index i)
+{
+  EIGEN_STATIC_ASSERT_VECTOR_ONLY(Derived);
+  eigen_assert(i<newSize);
+  derived().resize(newSize);
+  return setUnit(i);
+}
+
 } // end namespace Eigen
 
 #endif // EIGEN_CWISE_NULLARY_OP_H
diff --git a/Eigen/src/Core/MatrixBase.h b/Eigen/src/Core/MatrixBase.h
index 5786f76e0..11435903b 100644
--- a/Eigen/src/Core/MatrixBase.h
+++ b/Eigen/src/Core/MatrixBase.h
@@ -268,6 +268,8 @@ template<typename Derived> class MatrixBase
     Derived& setIdentity();
     EIGEN_DEVICE_FUNC
     Derived& setIdentity(Index rows, Index cols);
+    EIGEN_DEVICE_FUNC Derived& setUnit(Index i);
+    EIGEN_DEVICE_FUNC Derived& setUnit(Index newSize, Index i);
 
     bool isIdentity(const RealScalar& prec = NumTraits<Scalar>::dummy_precision()) const;
     bool isDiagonal(const RealScalar& prec = NumTraits<Scalar>::dummy_precision()) const;
diff --git a/doc/QuickReference.dox b/doc/QuickReference.dox
index 44f5410db..59d7d05e4 100644
--- a/doc/QuickReference.dox
+++ b/doc/QuickReference.dox
@@ -261,6 +261,8 @@ x.setIdentity();
 Vector3f::UnitX() // 1 0 0
 Vector3f::UnitY() // 0 1 0
 Vector3f::UnitZ() // 0 0 1
+Vector4f::Unit(i)
+x.setUnit(i);
 \endcode
   </td>
   <td>
@@ -278,6 +280,7 @@ N/A
 
 
 VectorXf::Unit(size,i)
+x.setUnit(size,i);
 VectorXf::Unit(4,1) == Vector4f(0,1,0,0)
                     == Vector4f::UnitY()
 \endcode
@@ -285,7 +288,12 @@ VectorXf::Unit(4,1) == Vector4f(0,1,0,0)
 </tr>
 </table>
 
-
+Note that it is allowed to call any of the \c set* functions to a dynamic-sized vector or matrix without passing new sizes.
+For instance:
+\code
+MatrixXi M(3,3);
+M.setIdentity();
+\endcode
 
 \subsection QuickRef_Map Mapping external arrays
 
diff --git a/test/nullary.cpp b/test/nullary.cpp
index acd55506e..22ec92352 100644
--- a/test/nullary.cpp
+++ b/test/nullary.cpp
@@ -191,6 +191,24 @@ void testVectorType(const VectorType& base)
       }
     }
   }
+
+  // test setUnit()
+  if(m.size()>0)
+  {
+    for(Index k=0; k<10; ++k)
+    {
+      Index i = internal::random<Index>(0,m.size()-1);
+      m.setUnit(i);
+      VERIFY_IS_APPROX( m, VectorType::Unit(m.size(), i) );
+    }
+    if(VectorType::SizeAtCompileTime==Dynamic)
+    {
+      Index i = internal::random<Index>(0,2*m.size()-1);
+      m.setUnit(2*m.size(),i);
+      VERIFY_IS_APPROX( m, VectorType::Unit(m.size(),i) );
+    }
+  }
+
 }
 
 template<typename MatrixType>