diff --git a/include/rosa/agent/History.hpp b/include/rosa/agent/History.hpp
index 3e38494..a10bb1e 100644
--- a/include/rosa/agent/History.hpp
+++ b/include/rosa/agent/History.hpp
@@ -1,596 +1,613 @@
 //===-- rosa/agent/History.hpp ----------------------------------*- C++ -*-===//
 //
 //                                 The RoSA Framework
 //
 // Distributed under the terms and conditions of the Boost Software License 1.0.
 // See accompanying file LICENSE.
 //
 // If you did not receive a copy of the license file, see
 // http://www.boost.org/LICENSE_1_0.txt.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file rosa/agent/History.hpp
 ///
 /// \author David Juhasz (david.juhasz@tuwien.ac.at)
 ///
 /// \date 2017
 ///
 /// \brief Definition of *history* *functionality*.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef ROSA_AGENT_HISTORY_HPP
 #define ROSA_AGENT_HISTORY_HPP
 
 #include "rosa/agent/Functionality.h"
 
 #include "rosa/config/config.h"
 
 #include "rosa/support/debug.hpp"
 #include "rosa/support/type_helper.hpp"
 
 #include <algorithm>
 #include <array>
 #include <limits>
 #include <vector>
 
+#include <math.h>
+
 namespace rosa {
 namespace agent {
 
 // @benedikt: todo: assert in history, which checks if push_back worked
 
 /// Retention policies defining what a \c rosa::agent::History instance should
 /// do when the number of recorded entries reached its capacity.
 enum class HistoryPolicy {
   SRWF, ///< Stop Recording When Full -- no new entry is recorded when full
   FIFO, ///< First In First Out -- overwrite the earliest entry with a new one
   LIFO  ///< Last In First Out -- overwrite the latest entry with a new one
 };
 
 template <typename T, HistoryPolicy P> class History : public Functionality {
 
 public:
   History(void) noexcept = default;
 
   /// Destroys \p this object.
   virtual ~History(void) = default;
 
   /// Tells the retention policy applied to \p this object.
   ///
   /// \return \c rosa::agent::History::P
   static constexpr HistoryPolicy policy(void) noexcept { return P; }
 
   /// Tells how many entries may be recorded by \c this object.
   ///
   /// \note The number of entries that are actually recorded may be smaller.
   ///
   /// \return The max number of entries that may be recorded
   virtual size_t maxLength(void) const noexcept = 0;
 
   /// Tells how many entries are currently recorded by \p this object.
   ///
   /// \return number of entries currently recorded by \p this object.
   ///
   /// \post The returned value cannot be larger than the capacity of \p this
   /// object:\code
   /// 0 <= numberOfEntries() && numberOfEntries <= lengthOfHistory()
   /// \endcode
   virtual size_t numberOfEntries(void) const noexcept = 0;
 
   /// Tells if \p this object has not recorded anything yet.
   ///
   /// \return if \p this object has no entries recorded
   bool empty(void) const noexcept { return numberOfEntries() == 0; }
 
   /// Tells if the history reached it's maximum length
   ///
   /// \return if the history reached it's maximum length.
   bool full(void) const noexcept { return numberOfEntries() == maxLength(); }
 
   /// Gives a constant lvalue reference to an entry stored in \p this object.
   ///
   /// \note The recorded entries are indexed starting from the latest one.
   ///
   /// \param I the index at which the stored entry to take from
   ///
   /// \pre \p I is a valid index:\code
   /// 0 <= I && I < numberOfEntries()
   /// \endcode
   virtual const T &entry(const size_t I = 0) const noexcept = 0;
 
   /// Removes all entries recorded in \p this object.
   virtual void clear() noexcept = 0;
 
 private:
   /// Pushes a new entry into the history.
   ///
   /// \note The earliest entry gets overwritten if the history is full.
   ///
   /// \param V value to push into the history
   virtual void pushBack(const T &V) noexcept = 0;
 
   /// Replaces the most recent entry in the history.
   ///
   /// \param V value to replace the most current value with
   virtual void replaceFront(const T &V) noexcept = 0;
 
 public:
   /// Adds a new entry to \p this object and tells if the operation was
   /// successful.
   ///
   /// \note Success of the operation depends on the actual policy.
   ///
   /// \param V value to store
   ///
   /// \return if \p V was successfully stored
   bool addEntry(const T &V) noexcept {
     switch (P) {
     default:
       ROSA_CRITICAL("unkown HistoryPolicy");
     case HistoryPolicy::LIFO:
       if (full()) {
         replaceFront(V);
         return true;
       }
     case HistoryPolicy::SRWF:
       if (full()) {
         return false;
       }
     // \note Fall through to FIFO which unconditionally pushes the new entry.
     case HistoryPolicy::FIFO:
       // FIFO and SRWF not full.
       pushBack(V);
       return true;
     }
   }
 
   /// Tells the trend set by the entries recorded by \p this object.
   ///
   /// The number of steps to go back when calculating the trend is defined as
   /// argument to the function.
   ///
   /// \note The number of steps that can be made is limited by the number of
   /// entries recorded by \p this object.
   ///
   /// \note The function is made a template only to be able to use
   /// \c std::enable_if.
   ///
   /// \tparam X always use the default!
   ///
   /// \param D number of steps to go back in *history*
   ///
   /// \return trend set by analyzed entries
   ///
   /// \pre Statically, \p this object stores signed arithmetic values:\code
   /// std::is_arithmetic<T>::value && std::is_signed<T>::value
   /// \endcode Dynamically, \p D is a valid number of steps to take:\code
   /// 0 <= D && D < lengthOfHistory()
   /// \endcode
   template <typename X = T>
   typename std::enable_if<
       std::is_arithmetic<X>::value && std::is_signed<X>::value, X>::type
   trend(const size_t D) const noexcept {
     STATIC_ASSERT((std::is_same<X, T>::value), "not default template arg");
     ASSERT(0 <= D && D < maxLength()); // Boundary check.
     if (numberOfEntries() < 2 || D < 1) {
       // No entries for computing trend.
       return {}; // Zero element of \p T
     } else {
       // Here at least two entries.
       // \c S is the number of steps that can be done.
       const size_t S = std::min(numberOfEntries() - 1, D);
       size_t I = S;
 
       // Compute trend with linear regression.
       size_t SumIndices = 0;
       T SumEntries = {};
       T SumSquareEntries = {};
       T SumProduct = {};
       while (I > 0) {
         // \note Indexing for the regression starts in the past.
         const size_t Index = S - I;
         const T Entry = entry(--I);
         SumIndices += Index;
         SumEntries += Entry;
         SumSquareEntries += Entry * Entry;
         SumProduct += Entry * Index;
       }
 
       return (SumProduct * S - SumEntries * SumIndices) /
              (SumSquareEntries * S - SumEntries * SumEntries);
     }
   }
 
   /// Tells the average absolute difference between consecutive entries recorded
   /// by \p this object
   /// The number of steps to go back when calculating the average is defined as
   /// argument to the function.
   ///
   /// \note The number of steps that can be made is limited by the number of
   /// entries recorded by \p this object.
   ///
   /// \note The function is made a template only to be able to use
   /// \c std::enable_if.
   ///
   /// \tparam X always use the default!
   ///
   /// \param D number of steps to go back in *history*
   ///
   /// \pre Statically, \p this object stores arithmetic values:\code
   /// std::is_arithmetic<T>::value
   /// \endcode Dynamically, \p D is a valid number of steps to take:\code
   /// 0 <= D && D < lengthOfHistory()
   /// \endcode
   template <typename X = T>
   typename std::enable_if<std::is_arithmetic<X>::value, size_t>::type
   averageAbsDiff(const size_t D) const noexcept {
     STATIC_ASSERT((std::is_same<X, T>::value), "not default template arg");
     ASSERT(0 <= D && D < maxLength()); // Boundary check.
     if (numberOfEntries() < 2 || D < 1) {
       // No difference to average.
       return {}; // Zero element of \p T
     } else {
       // Here at least two entries.
       // \c S is the number of steps that can be done.
       const size_t S = std::min(numberOfEntries() - 1, D);
 
       // Sum up differences as non-negative values only, hence using an
       // unsigned variable for that.
       size_t Diffs = {}; // Init to zero.
       // Count down entry indices and sum up all the absolute differences.
       size_t I = S;
       T Last = entry(I);
       while (I > 0) {
         T Next = entry(--I);
         Diffs += Last < Next ? Next - Last : Last - Next;
         Last = Next;
       }
       // Return the average of the summed differences.
       return Diffs / S;
     }
   }
 
   /// Tells the average of all entries recorded by \p this object
   ///
   /// \tparam R type of the result
   template <typename R> R average() const noexcept {
     R Average = 0;
     for (size_t I = 0; I < numberOfEntries(); I++) {
       Average += entry(I);
     }
     Average /= numberOfEntries();
     return Average;
   }
 
+  /// Tells the sigma of all entries recorded by \p this object
+  ///
+  /// \tparam R type of the result
+  template <typename R> R sigma() const noexcept {
+    R Average = average();
+    R Sigma = 0;
+    for (size_t I = 0; I < numberOfEntries(); I++) {
+      Sigma += pow((entry(I)-Average),2);
+    }
+    Sigma = sqrt(1.0/numberOfEntries()*Sigma);
+    return Sigma;
+  }
+
   // Experiment
+  // Note from Benedikt: I think this will not return the median because the
+  // history is not sorted
   template <typename R> R median() const noexcept {
     if (numberOfEntries() % 2 == 0) {
       return (entry(numberOfEntries() / 2 - 1) + entry(numberOfEntries() / 2)) /
              2;
     } else {
       return entry(numberOfEntries() / 2);
     }
   }
 };
 
 /// Implements *history* by recording and storing values.
 /// The length of the underlying std::array is static and must be set at
 /// compile-time
 ///
 /// \note Not thread-safe implementation, which should not be a problem as any
 /// instance of \c rosa::agent::Functionality is an internal component of a
 /// \c rosa::Agent, which is the basic unit of concurrency.
 ///
 /// \tparam T type of values to store
 /// \tparam N number of values to store at most
 /// \tparam P retention policy to follow when capacity is reached
 ///
 /// \invariant The size of the underlying \c std::array is `N + 1`:\code
 /// max_size() == N + 1 && N == max_size() - 1
 /// \endcode
 template <typename T, size_t N, HistoryPolicy P>
 class StaticLengthHistory : public History<T, P>, private std::array<T, N + 1> {
 
   // Bring into scope inherited functions that are used.
   using std::array<T, N + 1>::max_size;
   using std::array<T, N + 1>::operator[];
 
   /// The index of the first data element in the circular buffer.
   size_t Data;
 
   /// The index of the first empty slot in the circular buffer.
   size_t Space;
 
 public:
   using History<T, P>::policy;
   using History<T, P>::empty;
   using History<T, P>::full;
   using History<T, P>::addEntry;
   using History<T, P>::trend;
   using History<T, P>::averageAbsDiff;
 
   /// Creates an instances by initializing the indices for the circular buffer.
   StaticLengthHistory(void) noexcept : Data(0), Space(0) {}
 
   /// Destroys \p this object.
   ~StaticLengthHistory(void) override = default;
 
   /// Tells how many entries may be recorded by \c this object.
   ///
   /// \note The number of entries that are actually recorded may be smaller.
   ///
   /// \return \c rosa::agent::History::N
   size_t maxLength(void) const noexcept override { return N; }
 
   /// Tells how many entries are currently recorded by \p this object.
   ///
   /// \return number of entries currently recorded by \p this object.
   ///
   /// \post The returned value cannot be larger than the capacity of \p this
   /// object:\code
   /// 0 <= numberOfEntries() && numberOfEntries <= lengthOfHistory()
   /// \endcode
   size_t numberOfEntries(void) const noexcept override {
     return Data <= Space ? Space - Data : max_size() - Data + Space;
   }
 
   /// Gives a constant lvalue reference to an entry stored in \p this object.
   ///
   /// \note The recorded entries are indexed starting from the latest one.
   ///
   /// \param I the index at which the stored entry to take from
   ///
   /// \pre \p I is a valid index:\code
   /// 0 <= I && I < numberOfEntries()
   /// \endcode
   const T &entry(const size_t I = 0) const noexcept override {
     ASSERT(0 <= I && I < numberOfEntries()); // Boundary check.
     // Position counted back from the last recorded entry.
     typename std::make_signed<const size_t>::type Pos = Space - (1 + I);
     // Actual index wrapped around to the end of the buffer if negative.
     return (*this)[Pos >= 0 ? Pos : max_size() + Pos];
   }
 
   /// Removes all entries recorded in \p this object.
   void clear() noexcept override {
     Data = 0;
     Space = 0;
   }
 
 private:
   /// Pushes a new entry into the circular buffer.
   ///
   /// \note The earliest entry gets overwritten if the buffer is full.
   ///
   /// \param V value to push into the buffer
   void pushBack(const T &V) noexcept override {
     // Store value to the first empty slot and step Space index.
     (*this)[Space] = V;
     Space = (Space + 1) % max_size();
     if (Data == Space) {
       // Buffer was full, step Data index.
       Data = (Data + 1) % max_size();
     }
   }
 
   /// Replaces the most recent entry in the history.
   ///
   /// \param V value to replace the most current value with
   void replaceFront(const T &V) noexcept override {
     (*this)[(Space - 1) % max_size()] = V;
   }
 };
 
 /// Adds a new entry to a \c rosa::agent::History instance.
 ///
 /// \note The result of \c rosa::agent::History::addEntry is ignored.
 ///
 /// \tparam T type of values stored in \p H
 /// \tparam N number of values \p H is able to store
 /// \tparam P retention policy followed by \p H when capacity is reached
 ///
 /// \param H to add a new entry to
 /// \param V value to add to \p H
 ///
 /// \return \p H after adding \p V to it
 template <typename T, size_t N, HistoryPolicy P>
 StaticLengthHistory<T, N, P> &operator<<(StaticLengthHistory<T, N, P> &H,
                                          const T &V) noexcept {
   H.addEntry(V);
   return H;
 }
 
 /// Implements *DynamicLengthHistory* by recording and storing values.
 ///
 /// \note Not thread-safe implementation, which should not be a problem as any
 /// instance of \c rosa::agent::Functionality is an internal component of a
 /// \c rosa::Agent, which is the basic unit of concurrency.
 ///
 /// \tparam T type of values to store
 /// \tparam P retention policy to follow when capacity is reached
 template <typename T, HistoryPolicy P>
 class DynamicLengthHistory : public History<T, P>, private std::vector<T> {
 
 private:
   // Bring into scope inherited functions that are used.
   using std::vector<T>::size;
   using std::vector<T>::resize;
   using std::vector<T>::push_back;
   using std::vector<T>::pop_back;
   using std::vector<T>::max_size;
   /// The current length of the DynamicLengthHistory.
   size_t Length;
 
 public:
   // Bring into scope inherited functions that are used.
   using std::vector<T>::erase;
   using std::vector<T>::begin;
   using std::vector<T>::end;
   using std::vector<T>::rbegin;
   using std::vector<T>::rend;
   using std::vector<T>::operator[];
 
   // Bring into scope inherited functions that are used.
   using History<T, P>::policy;
   using History<T, P>::empty;
   using History<T, P>::full;
   using History<T, P>::addEntry;
   using History<T, P>::trend;
   using History<T, P>::averageAbsDiff;
 
   /// Creates an instances by setting an initial length
   DynamicLengthHistory(size_t Length) noexcept : Length(Length) {}
 
   /// Destroys \p this object.
   ~DynamicLengthHistory(void) override = default;
 
   /// Tells how many entries may be recorded by \c this object.
   ///
   /// \note The number of entries that are actually recorded may be smaller.
   ///
   /// \return \c rosa::agent::DynamicLengthHistory::N
   size_t maxLength(void) const noexcept override { return Length; }
 
   /// Tells how many entries are currently recorded by \p this object.
   ///
   /// \return number of entries currently recorded by \p this object.
   ///
   /// \post The returned value cannot be larger than the capacity of \p this
   /// object:\code
   /// 0 <= numberOfEntries() && numberOfEntries <=
   /// lengthOfHistory() \endcode
   size_t numberOfEntries(void) const noexcept override { return size(); }
 
   /// Gives a constant lvalue reference to an entry stored in \p this object.
   ///
   /// \note The recorded entries are indexed starting from the latest one.
   ///
   /// \param I the index at which the stored entry to take from
   ///
   /// \pre \p I is a valid index:\code
   /// 0 <= I && I < numberOfEntries()
   /// \endcode
   const T &entry(const size_t I = 0) const noexcept override {
     ASSERT(0 <= I && I < numberOfEntries()); // Boundary check.
     return this->operator[](size() - I - 1);
   }
 
   /// Removes all entries recorded in \p this object.
   void clear() noexcept override { erase(begin(), end()); }
 
   /// Sort all entries in ascending order.
   void sortAscending(void) noexcept { std::sort(begin(), end()); }
 
   /// Sort all entries in descending order.
   void sortDescending(void) noexcept { std::sort(rbegin(), rend()); }
 
   /// Delets one element of the history.
   ///
   /// \param V the element which shall be deleted.
   void deleteEntry(T &V) {
     auto it = std::find(begin(), end(), V);
 
     if (it != end()) {
       erase(it);
     }
   }
 
   /// Gives back the lowest entry of the history.
   ///
   /// \return the lowest entry. In case of an empty history, the maximum value
   /// of the chosen data type is returned.
   T lowestEntry() {
     auto it = std::min_element(begin(), end());
 
     if (it == end()) {
       return std::numeric_limits<T>::max();
     } else {
       return *it;
     }
   }
 
   /// Gives back the highest entry of the history.
   ///
   /// \return the highest entry. In case of an empty history, the minimum value
   /// of the chosen data type is returned.
   T highestEntry() {
     auto it = std::max_element(begin(), end());
 
     if (it == end()) {
       return std::numeric_limits<T>::min();
     } else {
       return *it;
     }
   }
 
 private:
   /// Pushes a new entry into the circular buffer.
   ///
   /// \note The earliest entry gets overwritten if the buffer is full.
   ///
   /// \param V value to push into the buffer
   void pushBack(const T &V) noexcept override {
     if (full()) {
       erase(begin());
     }
     push_back(V);
   }
 
   /// Replaces the most recent entry in the history.
   ///
   /// \param V value to replace the most current value with
   void replaceFront(const T &V) noexcept override {
     (void)pop_back();
     push_back(V);
   }
 
 public:
   /// Resizes the History length. If the new length is smaller than the number
   /// of currently stored values, values are deleted according to the
   /// HistoryPolicy.
   ///
   /// @param NewLength The new Length of the History.
   void setLength(size_t NewLength) noexcept {
     Length = NewLength;
     if (NewLength < numberOfEntries()) {
       switch (P) {
       default:
         ROSA_CRITICAL("unkown HistoryPolicy");
       case HistoryPolicy::LIFO:
       case HistoryPolicy::SRWF:
         // Delete last numberOfEntries() - NewLength items from the back
         erase(begin() + NewLength, end());
         break;
       case HistoryPolicy::FIFO:
         // Delete last numberOfEntries() - NewLength items from the front
         erase(begin(), begin() + (numberOfEntries() - NewLength));
         break;
       }
     }
     this->resize(Length);
   }
 };
 
 /// Adds a new entry to a \c rosa::agent::DynamicLengthHistory instance.
 ///
 /// \note The result of \c rosa::agent::DynamicLengthHistory::addEntry is
 /// ignored.
 ///
 /// \tparam T type of values stored in \p H
 /// \tparam P retention policy followed by \p H when capacity is reached
 ///
 /// \param H to add a new entry to
 /// \param V value to add to \p H
 ///
 /// \return \p H after adding \p V to it
 template <typename T, HistoryPolicy P>
 DynamicLengthHistory<T, P> &operator<<(DynamicLengthHistory<T, P> &H,
                                        const T &V) noexcept {
   H.addEntry(V);
   return H;
 }
 } // End namespace agent
 } // End namespace rosa
 
 #endif // ROSA_AGENT_HISTORY_HPP