diff --git a/latan/XYSampleData.cpp b/latan/XYSampleData.cpp
new file mode 100644
index 0000000..a6f6cac
--- /dev/null
+++ b/latan/XYSampleData.cpp
@@ -0,0 +1,294 @@
+/*
+ * XYSampleData.cpp, part of LatAnalyze 3
+ *
+ * Copyright (C) 2013 - 2014 Antonin Portelli
+ *
+ * LatAnalyze 3 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * LatAnalyze 3 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with LatAnalyze 3.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <latan/XYSampleData.hpp>
+#include <latan/includes.hpp>
+
+using namespace std;
+using namespace Latan;
+
+/******************************************************************************
+ *                      SampleFitResult implementation                        *
+ ******************************************************************************/
+double SampleFitResult::getChi2(const Index s) const
+{
+    return chi2_[s];
+}
+
+const DSample & SampleFitResult::getChi2(const PlaceHolder ph __unused) const
+{
+    return chi2_;
+}
+
+double SampleFitResult::getChi2PerDof(const Index s) const
+{
+    return chi2_[s]/static_cast<double>(nDof_);
+}
+
+DSample SampleFitResult::getChi2PerDof(const PlaceHolder ph __unused) const
+{
+    return chi2_/static_cast<double>(nDof_);
+}
+const DoubleFunction & SampleFitResult::getModel(const Index s, 
+                                                 const Index j) const
+{
+    return model_[static_cast<unsigned int>(j)][s];
+}
+                                    
+const DoubleFunctionSample & SampleFitResult::getModel(
+                                                const PlaceHolder ph __unused,
+                                                const Index j) const
+{
+    return model_[static_cast<unsigned int>(j)];
+}
+
+/******************************************************************************
+ *                       XYSampleData implementation                          *
+ ******************************************************************************/
+// constructors ////////////////////////////////////////////////////////////////
+XYSampleData::XYSampleData(const Index nData, const Index xDim, 
+                           const Index yDim, const Index nSample)
+{
+    resize(nData, xDim, yDim, nSample);
+}
+
+// access //////////////////////////////////////////////////////////////////////
+const XYStatData & XYSampleData::getData(const Index s)
+{
+    setDataToSample(s);
+    
+    return data_;
+}
+
+void XYSampleData::resize(const Index nData, const Index xDim,
+                          const Index yDim, const Index nSample)
+{
+    FitInterface::resize(nData, xDim, yDim);
+    x_.resize(nSample);
+    x_.resizeMat(nData, xDim);
+    y_.resize(nSample);
+    y_.resizeMat(nData, yDim);
+    data_.resize(nData, xDim, yDim);
+    isCovarianceInit_ = false;
+}
+
+XYSampleData::SampleBlock XYSampleData::x(const PlaceHolder ph1 __unused,
+                                          const PlaceHolder ph2 __unused)
+{
+    isCovarianceInit_ = false;
+    
+    return x_.block(0, 0, getNData(), getXDim());
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::x(const PlaceHolder ph1 __unused,
+                                               const PlaceHolder ph2 __unused)
+                                               const
+{
+    return x_.block(0, 0, getNData(), getXDim());
+}
+
+XYSampleData::SampleBlock XYSampleData::x(const Index i, 
+                                          const PlaceHolder ph2 __unused)
+{
+    isCovarianceInit_ = false;
+    
+    return x_.block(0, i, getNData(), 1);
+}
+                                          
+XYSampleData::ConstSampleBlock XYSampleData::x(const Index i,
+                                               const PlaceHolder ph2 __unused)
+                                               const
+{
+    return x_.block(0, i, getNData(), 1);
+}
+
+XYSampleData::SampleBlock XYSampleData::x(const PlaceHolder ph1 __unused,
+                                          const Index k)
+{
+    isCovarianceInit_ = false;
+    
+    return x_.block(k, 0, 1, getXDim());
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::x(const PlaceHolder ph1 __unused,
+                                               const Index k) const
+{
+    return x_.block(k, 0, 1, getXDim());
+}
+
+XYSampleData::SampleBlock XYSampleData::x(const Index i, const Index k)
+{
+    isCovarianceInit_ = false;
+    
+    return x_.block(k, i, 1, 1);
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::x(const Index i, const Index k)   
+                                               const
+{
+    return x_.block(k, i, 1, 1);
+}
+
+XYSampleData::SampleBlock XYSampleData::y(const PlaceHolder ph1 __unused,
+                                          const PlaceHolder ph2 __unused)
+{
+    isCovarianceInit_ = false;
+    
+    return y_.block(0, 0, getNData(), getXDim());
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::y(const PlaceHolder ph1 __unused,
+                                               const PlaceHolder ph2 __unused)
+                                               const
+{
+    return y_.block(0, 0, getNData(), getXDim());
+}
+
+XYSampleData::SampleBlock XYSampleData::y(const Index j, 
+                                          const PlaceHolder ph2 __unused)
+{
+    isCovarianceInit_ = false;
+    
+    return y_.block(0, j, getNData(), 1);
+}
+                                          
+XYSampleData::ConstSampleBlock XYSampleData::y(const Index j,
+                                               const PlaceHolder ph2 __unused)
+                                               const
+{
+    return y_.block(0, j, getNData(), 1);
+}
+
+XYSampleData::SampleBlock XYSampleData::y(const PlaceHolder ph1 __unused,
+                                          const Index k)
+{
+    isCovarianceInit_ = false;
+    
+    return y_.block(k, 0, 1, getXDim());
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::y(const PlaceHolder ph1 __unused,
+                                               const Index k) const
+{
+    return y_.block(k, 0, 1, getXDim());
+}
+
+XYSampleData::SampleBlock XYSampleData::y(const Index j, const Index k)
+{
+    isCovarianceInit_ = false;
+    
+    return y_.block(k, j, 1, 1);
+}
+
+XYSampleData::ConstSampleBlock XYSampleData::y(const Index j, const Index k)   
+                                               const
+{
+    return y_.block(k, j, 1, 1);
+}
+
+// fit /////////////////////////////////////////////////////////////////////////
+SampleFitResult XYSampleData::fit(
+                    const std::vector<const DoubleModel *> &modelVector,
+                    Minimizer &minimizer, const DVec &init,
+                    const FitVerbosity verbosity)
+{
+    const Index     nSample = x_.size();
+    FitResult       sampleResult;
+    SampleFitResult result;
+    bool            initChi2;
+    
+    // copy interface to sample data
+    data_.setFitInterface(*this);
+    
+    // sample loop
+    result.resize(nSample);
+    result.chi2_.resize(nSample);
+    FOR_STAT_ARRAY(x_, s)
+    {
+        // set data
+        setDataToSample(s);
+        
+        // initialize chi^2 only once
+        initChi2 = (s == central);
+        
+        // fit
+        sampleResult = data_.fit(modelVector, minimizer, init, initChi2,
+                                 verbosity);
+        
+        // store result
+        result[s]       = sampleResult;
+        result.chi2_[s] = sampleResult.getChi2();
+        result.nDof_    = sampleResult.getNDof();
+        result.model_.resize(modelVector.size());
+        for (unsigned int j = 0; j < modelVector.size(); ++j)
+        {
+            result.model_[j].resize(nSample);
+            result.model_[j][s] = sampleResult.getModel(j);
+        }
+    }
+    
+    return result;
+}
+
+SampleFitResult XYSampleData::fit(const DoubleModel &model,
+                                  Minimizer &minimizer,
+                                  const DVec &init,
+                                  const FitVerbosity verbosity)
+{
+    vector<const DoubleModel *> modelVector(1);
+    
+    modelVector[0] = &model;
+    
+    return fit(modelVector, minimizer, init, verbosity);
+}
+
+void XYSampleData::setDataToSample(const Index s)
+{
+    // compute covariance matrices if necessary
+    if (!isCovarianceInit_)
+    {
+        DMatSample buf1, buf2;
+            
+        for (Index i2 = 0; i2 < getXDim(); ++i2)
+        for (Index i1 = 0; i1 < getXDim(); ++i1)
+        {
+            buf1 = x(i1);
+            buf2 = x(i2);
+            data_.xxVar(i1, i2) = buf1.covarianceMatrix(buf2);
+        }
+        for (Index j2 = 0; j2 < getYDim(); ++j2)
+        for (Index j1 = 0; j1 < getYDim(); ++j1)
+        {
+            buf1 = y(j1);
+            buf2 = y(j2);
+            data_.yyVar(j1, j2) = buf1.covarianceMatrix(buf2);
+        }
+        for (Index i = 0; i < getXDim(); ++i)
+        for (Index j = 0; j < getYDim(); ++j)
+        {
+            buf1 = y(j);
+            buf2 = x(i);
+            data_.yxVar(j, i) = buf1.covarianceMatrix(buf2);
+        }
+        isCovarianceInit_ = true;
+    }
+    // set data
+    data_.x(_, _) = x_[s];
+    data_.y(_, _) = y_[s];
+}
diff --git a/latan/XYSampleData.hpp b/latan/XYSampleData.hpp
new file mode 100644
index 0000000..433e517
--- /dev/null
+++ b/latan/XYSampleData.hpp
@@ -0,0 +1,111 @@
+/*
+ * XYSampleData.hpp, part of LatAnalyze 3
+ *
+ * Copyright (C) 2013 - 2014 Antonin Portelli
+ *
+ * LatAnalyze 3 is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * LatAnalyze 3 is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with LatAnalyze 3.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef Latan_XYSampleData_hpp_
+#define Latan_XYSampleData_hpp_
+
+#include <latan/Global.hpp>
+#include <latan/FitInterface.hpp>
+#include <latan/Function.hpp>
+#include <latan/MatSample.hpp>
+#include <latan/Minimizer.hpp>
+#include <latan/XYStatData.hpp>
+
+BEGIN_NAMESPACE
+
+/******************************************************************************
+ *                            object for fit result                           *
+ ******************************************************************************/
+class SampleFitResult: public DMatSample
+{
+    friend class XYSampleData;
+public:
+    // constructors
+    using DMatSample::DMatSample;
+    SampleFitResult(void) = default;
+    // destructor
+    virtual ~SampleFitResult(void) = default;
+    // access
+    double                       getChi2(const Index s) const;
+    const DSample &              getChi2(const PlaceHolder ph = _) const;
+    double                       getChi2PerDof(const Index s) const;
+    DSample                      getChi2PerDof(const PlaceHolder ph = _) const;
+    const DoubleFunction &       getModel(const Index s,
+                                          const Index j = 0) const;
+    const DoubleFunctionSample & getModel(const PlaceHolder ph = _,
+                                          const Index j = 0) const;
+private:
+    DSample                           chi2_;
+    Index                             nDof_{0};
+    std::vector<DoubleFunctionSample> model_;
+};
+
+/******************************************************************************
+ *                            XYSampleData                                    *
+ ******************************************************************************/
+class XYSampleData: public FitInterface
+{
+public:
+    typedef DMatSample::Block      SampleBlock;
+    typedef DMatSample::ConstBlock ConstSampleBlock;
+public:
+    // constructors
+    XYSampleData(void) = default;
+    XYSampleData(const Index nData, const Index xDim, const Index yDim,
+                 const Index nSample);
+    // destructor
+    virtual ~XYSampleData(void) = default;
+    // access
+    const XYStatData & getData(const Index s = central);
+    void             resize(const Index nData, const Index xDim,
+                            const Index yDim, const Index nSample);
+    SampleBlock      x(const PlaceHolder ph1, const PlaceHolder ph2);
+    ConstSampleBlock x(const PlaceHolder ph1, const PlaceHolder ph2) const;
+    SampleBlock      x(const Index i, const PlaceHolder ph2 = _);
+    ConstSampleBlock x(const Index i, const PlaceHolder ph2 = _) const;
+    SampleBlock      x(const PlaceHolder ph1, const Index k);
+    ConstSampleBlock x(const PlaceHolder ph1, const Index k) const;
+    SampleBlock      x(const Index i, const Index k);
+    ConstSampleBlock x(const Index i, const Index k) const;
+    SampleBlock      y(const PlaceHolder ph1, const PlaceHolder ph2);
+    ConstSampleBlock y(const PlaceHolder ph1, const PlaceHolder ph2) const;
+    SampleBlock      y(const Index i, const PlaceHolder ph2 = _);
+    ConstSampleBlock y(const Index i, const PlaceHolder ph2 = _) const;
+    SampleBlock      y(const PlaceHolder ph1, const Index k);
+    ConstSampleBlock y(const PlaceHolder ph1, const Index k) const;
+    SampleBlock      y(const Index i, const Index k);
+    ConstSampleBlock y(const Index i, const Index k) const;
+    // fit
+    SampleFitResult fit(const std::vector<const DoubleModel *> &modelVector,
+                        Minimizer &minimizer, const DVec &init,
+                        const FitVerbosity verbosity = FitVerbosity::Silent);
+    SampleFitResult fit(const DoubleModel &model, Minimizer &minimizer,
+                        const DVec &init, 
+                        const FitVerbosity verbosity = FitVerbosity::Silent);
+private:
+    void setDataToSample(const Index s);
+private:
+    bool isCovarianceInit_;
+    DMatSample x_, y_;
+    XYStatData data_;
+};
+
+END_NAMESPACE
+
+#endif // Latan_XYSampleData_hpp_