diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1fb6b98..cad5465 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,8 +29,8 @@ endif()
 add_compile_options("-D_USE_MATH_DEFINES")
 
 # Eigen
-# set(Eigen_REQUIRED "eigen3 >= 3.3")
-# search_for_eigen()
+set(Eigen_REQUIRED "eigen3 >= 3.3")
+search_for_eigen()
 
 add_subdirectory(include)
 
diff --git a/include/Butterworth.h b/include/Butterworth.h
index b76d687..7689534 100644
--- a/include/Butterworth.h
+++ b/include/Butterworth.h
@@ -1,14 +1,14 @@
 #pragma once
 
 #include "GenericFilter.h"
+#include "typedefs.h"
 #include <complex>
-#include <vector>
 
 namespace fratio {
 
 // https://www.dsprelated.com/showarticle/1119.php
 template <typename T>
-class Butterworth : public GenericFilter<T> {
+class Butterworth : public DigitalFilter<T> {
 public:
     T PI = static_cast<T>(M_PI);
 
@@ -39,8 +39,9 @@ private:
     size_t m_order;
     T m_fc;
     T m_fs;
+    Eigen::VectorX<std::complex<T>> m_poles;
 };
 
 } // namespace fratio
 
-#include "Butterworth.inl"
\ No newline at end of file
+#include "Butterworth.tpp"
diff --git a/include/DigitalFilter.h b/include/DigitalFilter.h
index 903f5fa..0aec5c1 100644
--- a/include/DigitalFilter.h
+++ b/include/DigitalFilter.h
@@ -1,6 +1,8 @@
 #pragma once
 
 #include "GenericFilter.h"
+#include "typedefs.h"
+#include <vector>
 
 namespace fratio {
 
@@ -9,23 +11,18 @@ class DigitalFilter : public GenericFilter<T> {
 public:
     DigitalFilter() = default;
     DigitalFilter(const std::vector<T>& aCoeff, const std::vector<T>& bCoeff)
+    {
+        setCoeffs(aCoeff, bCoeff);
+    }
+    DigitalFilter(const Eigen::VectorX<T>& aCoeff, const Eigen::VectorX<T>& bCoeff)
         : GenericFilter<T>(aCoeff, bCoeff)
     {
     }
 
-    void setCoeff(const std::vector<double>& aCoeff, const std::vector<double>& bCoeff)
-    {
-        checkCoeff(aCoeff, bCoeff);
-
-        m_aCoeff = aCoeff;
-        m_bCoeff = bCoeff;
-        resetFilter();
-
-        normalize();
-    }
-
     size_t aOrder() const noexcept { return m_aCoeff.size(); }
     size_t bOrder() const noexcept { return m_bCoeff.size(); }
 };
 
-} // namespace fratio
\ No newline at end of file
+} // namespace fratio
+
+#include "DigitalFilter.tpp"
\ No newline at end of file
diff --git a/include/GenericFilter.h b/include/GenericFilter.h
index 106704b..787effe 100644
--- a/include/GenericFilter.h
+++ b/include/GenericFilter.h
@@ -1,7 +1,9 @@
 #pragma once
 
 #include "type_checks.h"
+#include "typedefs.h"
 #include <stddef.h>
+#include <string>
 #include <vector>
 
 namespace fratio {
@@ -11,29 +13,40 @@ class GenericFilter {
     static_assert(std::is_floating_point<T>::value && !std::is_const<T>::value, "Only accept non-complex floating point types.");
 
 public:
-    T stepFilter(T data);
-    std::vector<T> filter(const std::vector<T>& data);
+    static std::string filterStatus(FilterStatus status);
+
+public:
+    // Careful: Only an assert check for the filter status
+    T stepFilter(const T& data); 
+    Eigen::VectorX<T> filter(const Eigen::VectorX<T>& data);
+    bool getFilterResults(Eigen::Ref<Eigen::VectorX<T>> results, const Eigen::VectorX<T>& data);
     void resetFilter();
 
-    void getCoeff(std::vector<T>& aCoeff, std::vector<T>& bCoeff) const noexcept;
+    bool setCoeffs(const std::vector<T>& aCoeff, const std::vector<T>& bCoeff);
+    bool setCoeffs(const Eigen::VectorX<T>& aCoeff, const Eigen::VectorX<T>& bCoeff);
+    void getCoeffs(std::vector<T>& aCoeff, std::vector<T>& bCoeff) const;
+    void getCoeffs(Eigen::Ref<Eigen::VectorX<T>> aCoeff, Eigen::Ref<Eigen::VectorX<T>> bCoeff) const;
+    FilterStatus status() const noexcept { return m_status; }
 
 protected:
     GenericFilter() = default;
-    GenericFilter(const std::vector<T>& aCoeff, const std::vector<T>& bCoeff);
+    GenericFilter(const Eigen::VectorX<T>& aCoeff, const Eigen::VectorX<T>& bCoeff);
     virtual ~GenericFilter() = default;
 
-    void checkCoeff(const std::vector<T>& aCoeff, const std::vector<T>& bCoeff);
-    void normalize();
+    void normalizeCoeffs();
+    template <typename T2>
+    bool checkCoeffs(const T2& aCoeff, const T2& bCoeff);
 
 protected:
-    std::vector<T> m_aCoeff;
-    std::vector<T> m_bCoeff;
+    FilterStatus m_status;
+    Eigen::VectorX<T> m_aCoeff;
+    Eigen::VectorX<T> m_bCoeff;
 
 private:
-    std::vector<T> m_filteredData;
-    std::vector<T> m_rawData;
+    Eigen::VectorX<T> m_filteredData;
+    Eigen::VectorX<T> m_rawData;
 };
 
 } // namespace fratio
 
-#include "GenericFilter.inl"
\ No newline at end of file
+#include "GenericFilter.tpp"
diff --git a/include/MovingAverage.h b/include/MovingAverage.h
index fb90a07..9ebcb12 100644
--- a/include/MovingAverage.h
+++ b/include/MovingAverage.h
@@ -1,20 +1,27 @@
 #pragma once
 
-#include "GenericFilter.h"
+#include "DigitalFilter.h"
+#include "typedefs.h"
 
 namespace fratio {
 
 template <typename T>
-class MovingAverage : public GenericFilter<T> {
+class MovingAverage : public DigitalFilter<T> {
 public:
     MovingAverage() = default;
     MovingAverage(size_t windowSize)
-        : GenericFilter<T>({ 1 }, std::vector<T>(windowSize, T(1) / windowSize))
+        : DigitalFilter<T>(Eigen::VectorX<T>::Constant(1, T(1)), Eigen::VectorX<T>::Constant(windowSize, T(1) / windowSize)))
     {
     }
 
-    void setWindowSize(size_t windowSize) { setCoeff({ 1 }, std::vector<T>(windowSize, 1 / windowSize)); }
-    size_t windowSize() const noexcept { return m_bCoeff.size(); }
+    void setWindowSize(size_t windowSize) { setCoeffs(Eigen::VectorX<T>::Constant(1, T(1)), Eigen::VectorX<T>::Constant(windowSize, T(1) / windowSize)); }
+    size_t windowSize() const noexcept { return bOrder(); }
+        : DigitalFilter<T>(Eigen::VectorX<T>::Constant(1, T(1)), Eigen::VectorX<T>::Constant(windowSize, T(1) / windowSize)))
+    {
+    }
+
+    void setWindowSize(size_t windowSize) { setCoeffs(Eigen::VectorX<T>::Constant(1, T(1)), Eigen::VectorX<T>::Constant(windowSize, T(1) / windowSize)); }
+    size_t windowSize() const noexcept { return bOrder(); }
 };
 
-} // namespace fratio
\ No newline at end of file
+} // namespace fratio
diff --git a/include/polynome_functions.h b/include/polynome_functions.h
index 8b62ac2..b19b37c 100644
--- a/include/polynome_functions.h
+++ b/include/polynome_functions.h
@@ -1,8 +1,8 @@
 #pragma once
 
 #include "type_checks.h"
+#include "typedefs.h"
 #include <complex>
-#include <vector>
 
 namespace fratio {
 
@@ -11,21 +11,32 @@ struct VietaAlgo {
     static_assert(std::is_arithmetic<internal::complex_sub_type_t<T>>::value, "This struct can only accept arithmetic types or complex.");
 
     // Vieta's computation: https://en.wikipedia.org/wiki/Vieta%27s_formulas
-    static std::vector<T> polyCoeffFromRoot(const std::vector<T>& poles);
+    static Eigen::VectorX<T> polyCoeffFromRoot(const Eigen::VectorX<T>& poles);
 };
 
 template <typename T>
-std::vector<T> VietaAlgo<T>::polyCoeffFromRoot(const std::vector<T>& poles)
+Eigen::VectorX<T> VietaAlgo<T>::polyCoeffFromRoot(const Eigen::VectorX<T>& poles)
 {
-    std::vector<T> coeff(poles.size() + 1, 0);
-    coeff[0] = 1;
+    Eigen::VectorX<T> coeffs = Eigen::VectorX<T>::Zero(poles.size() + 1);
+    coeffs(0) = T(1);
     for (size_t i = 0; i < poles.size(); ++i) {
         for (size_t k = i + 1; k > 0; --k) {
-            coeff[k] = coeff[k] - poles[i] * coeff[k - 1];
+            coeffs(k) -= poles(i) * coeffs(k - 1);
         }
     }
+    // Check for equation c(k) = sum(i=k-1, poles.size() : p(i)) * c(k-1), k>=1
+    // size_t pSize = poles.size();
+    // for (size_t k = 1; k < coeffs.size(); ++k)
+    //     coeffs(k) -= poles.tail(pSize - (k - 1)).sum() * coeffs(k - 1);
 
-    return coeff;
+    // Maybe better
+    // T sum = poles.sum();
+    // for (size_t k = 1; k < coeffs.size(); ++k) {
+    //     coeffs(k) -= sum * coeffs(k - 1);
+    //     sum -= poles(k - 1);
+    // } 
+
+    return coeffs;
 }
 
-} // namespace fratio
\ No newline at end of file
+} // namespace fratio