diff --git a/core/include/Data/ArrayData.h b/core/include/Data/ArrayData.h
index 55fb8c5..a66b06f 100644
--- a/core/include/Data/ArrayData.h
+++ b/core/include/Data/ArrayData.h
@@ -98,14 +98,34 @@ public:
         return m_Data.at(0);
     }
 
-    // TODO Comment
+    /**
+     * Merges into the array data an other array data
+     * @param other the array data to merge with
+     * @param prepend if true, the other array data is inserted at the beginning, otherwise it is
+     * inserted at the end
+     * @remarks this method is only available for a unidimensional ArrayData
+     */
     template <int D = Dim, typename = std::enable_if_t<D == 1> >
-    void merge(const ArrayData<1> &arrayData)
+    void add(const ArrayData<1> &other, bool prepend = false)
     {
         QWriteLocker locker{&m_Lock};
         if (!m_Data.empty()) {
-            QReadLocker otherLocker{&arrayData.m_Lock};
-            m_Data[0] += arrayData.data();
+            QReadLocker otherLocker{&other.m_Lock};
+
+            if (prepend) {
+                const auto &otherData = other.data();
+                const auto otherDataSize = otherData.size();
+
+                auto &data = m_Data[0];
+                data.insert(data.begin(), otherDataSize, 0.);
+
+                for (auto i = 0; i < otherDataSize; ++i) {
+                    data.replace(i, otherData.at(i));
+                }
+            }
+            else {
+                m_Data[0] += other.data();
+            }
         }
     }
 
diff --git a/core/include/Data/DataSeries.h b/core/include/Data/DataSeries.h
index 7e22a94..f6cbde5 100644
--- a/core/include/Data/DataSeries.h
+++ b/core/include/Data/DataSeries.h
@@ -49,18 +49,64 @@ public:
         m_ValuesData->clear();
     }
 
-    /// @sa IDataSeries::merge()
+    /// Merges into the data series an other data series
+    /// @remarks the data series to merge with is cleared after the operation
     void merge(IDataSeries *dataSeries) override
     {
-        if (auto dimDataSeries = dynamic_cast<DataSeries<Dim> *>(dataSeries)) {
-            m_XAxisData->merge(*dimDataSeries->xAxisData());
-            m_ValuesData->merge(*dimDataSeries->valuesData());
-            dimDataSeries->clear();
+        dataSeries->lockWrite();
+        lockWrite();
+
+        if (auto other = dynamic_cast<DataSeries<Dim> *>(dataSeries)) {
+            const auto &otherXAxisData = other->xAxisData()->cdata();
+            const auto &xAxisData = m_XAxisData->cdata();
+
+            // As data series are sorted, we can improve performances of merge, by call the sort
+            // method only if the two data series overlap.
+            if (!otherXAxisData.empty()) {
+                auto firstValue = otherXAxisData.front();
+                auto lastValue = otherXAxisData.back();
+
+                auto xAxisDataBegin = xAxisData.cbegin();
+                auto xAxisDataEnd = xAxisData.cend();
+
+                bool prepend;
+                bool sortNeeded;
+
+                if (std::lower_bound(xAxisDataBegin, xAxisDataEnd, firstValue) == xAxisDataEnd) {
+                    // Other data series if after data series
+                    prepend = false;
+                    sortNeeded = false;
+                }
+                else if (std::upper_bound(xAxisDataBegin, xAxisDataEnd, lastValue)
+                         == xAxisDataBegin) {
+                    // Other data series if before data series
+                    prepend = true;
+                    sortNeeded = false;
+                }
+                else {
+                    // The two data series overlap
+                    prepend = false;
+                    sortNeeded = true;
+                }
+
+                // Makes the merge
+                m_XAxisData->add(*other->xAxisData(), prepend);
+                m_ValuesData->add(*other->valuesData(), prepend);
+
+                if (sortNeeded) {
+                    sort();
+                }
+            }
+
+            // Clears the other data series
+            other->clear();
         }
         else {
             qCWarning(LOG_DataSeries())
-                << QObject::tr("Dection of a type of IDataSeries we cannot merge with !");
+                << QObject::tr("Detection of a type of IDataSeries we cannot merge with !");
         }
+        unlock();
+        dataSeries->unlock();
     }
 
     virtual void lockRead() { m_Lock.lockForRead(); }
diff --git a/core/src/Variable/Variable.cpp b/core/src/Variable/Variable.cpp
index 286ef52..c866661 100644
--- a/core/src/Variable/Variable.cpp
+++ b/core/src/Variable/Variable.cpp
@@ -55,11 +55,7 @@ void Variable::setDataSeries(std::shared_ptr<IDataSeries> dataSeries) noexcept
         impl->m_DataSeries = dataSeries->clone();
     }
     else {
-        dataSeries->lockWrite();
-        impl->m_DataSeries->lockWrite();
         impl->m_DataSeries->merge(dataSeries.get());
-        impl->m_DataSeries->unlock();
-        dataSeries->unlock();
         //  emit updated();
     }
 }