improve doxygen documentation of PPrepFourier.*

src/include/PPrepFourier.h

@@ -40,50 +40,168 @@
 
 //----------------------------------------------------------------------------
 /**
- * <p>Data structure holding raw time domain uSR data together with some
- * necessary meta information.
+ * \brief Data structure holding raw time-domain μSR data with metadata.
+ *
+ * This structure packages raw histogram data together with essential metadata
+ * needed for Fourier transform preparation. It includes timing information,
+ * t0 calibration, and time range specifications for selective data processing.
+ *
+ * \see PPrepFourier for the class that processes this data
  */
 struct musrFT_data {
-  Int_t dataSetTag;        ///< tag to label the data set. Needed for average-per-data-set
-  TString info;            ///< keeps all the meta information
-  Double_t timeResolution; ///< time resolution in (usec)
-  Int_t t0;                ///< keep the t0 bin
-  Double_t timeRange[2];   ///< time range to be used, given in (usec).
-  PDoubleVector rawData;   ///< a single time domain data vector
+  Int_t dataSetTag;        ///< Data set identifier tag (needed for average-per-data-set operations)
+  TString info;            ///< Metadata string (run name, histogram info, etc.)
+  Double_t timeResolution; ///< Time resolution in microseconds (μs)
+  Int_t t0;                ///< Time zero bin number (start of valid data)
+  Double_t timeRange[2];   ///< Time range to process: [0]=start, [1]=end in microseconds (μs)
+  PDoubleVector rawData;   ///< Raw time-domain data vector (bin counts)
 };
 
 //----------------------------------------------------------------------------
 /**
- * <p>Little helper class to prepare time-domain data for Fourier transform, without
- * theory, etc.
+ * \brief Prepares time-domain μSR data for Fourier transformation.
+ *
+ * PPrepFourier is a utility class that processes raw time-domain μSR data
+ * before Fourier transformation. It performs essential preprocessing steps:
+ * - Background correction (using range or explicit values)
+ * - Data rebinning/packing for improved statistics
+ * - Muon lifetime correction for theory-free analysis
+ * - Time range selection
+ *
+ * The class handles multiple data sets simultaneously and prepares them
+ * for subsequent Fourier analysis without requiring theoretical fit functions.
+ *
+ * \par Usage Example:
+ * \code
+ * PPrepFourier prep(packing, bkgRange, bkgValues);
+ * prep.AddData(dataSet1);
+ * prep.AddData(dataSet2);
+ * prep.DoBkgCorrection();
+ * prep.DoPacking();
+ * prep.DoLifeTimeCorrection(1.0);
+ * std::vector<TH1F*> histos = prep.GetData();
+ * \endcode
+ *
+ * \see musrFT_data for the input data structure
  */
 class PPrepFourier {
   public:
+    /// Default constructor (requires separate configuration)
     PPrepFourier();
+
+    /**
+     * \brief Full constructor with all configuration parameters.
+     * \param packing Rebinning factor (1=no rebinning, 2=combine 2 bins, etc.)
+     * \param bkgRange Background range [start, end] in bins (-1 if not used)
+     * \param bkg Vector of explicit background values (one per data set)
+     */
     PPrepFourier(const Int_t packing, const Int_t *bkgRange, PDoubleVector bkg);
+
+    /// Destructor
     virtual ~PPrepFourier();
 
+    /**
+     * \brief Sets background range for automatic background calculation.
+     * \param bkgRange Array [start, end] specifying background bins (both ≥-1)
+     */
     virtual void SetBkgRange(const Int_t *bkgRange);
+
+    /**
+     * \brief Sets explicit background values for each data set.
+     * \param bkg Vector of background values (one per histogram)
+     */
     virtual void SetBkg(PDoubleVector bkg);
+
+    /**
+     * \brief Sets rebinning/packing factor for data reduction.
+     * \param packing Number of bins to combine (must be > 0)
+     */
     virtual void SetPacking(const Int_t packing);
+
+    /**
+     * \brief Adds a time-domain data set for processing.
+     * \param data musrFT_data structure containing raw data and metadata
+     */
     virtual void AddData(musrFT_data &data);
+
+    /**
+     * \brief Applies background correction to all data sets.
+     *
+     * Uses either the background range (averaged over range) or explicit
+     * background values. Background is subtracted from all data points.
+     */
     virtual void DoBkgCorrection();
+
+    /**
+     * \brief Applies rebinning/packing to reduce data points.
+     *
+     * Combines adjacent bins according to the packing factor to improve
+     * statistics and reduce the number of data points.
+     */
     virtual void DoPacking();
+
+    /**
+     * \brief Applies muon lifetime correction for theory-free analysis.
+     * \param fudge Rescaling factor for estimated N0 (typically ~1.0)
+     *
+     * Multiplies data by exp(t/τ) to remove muon decay, estimates N0 from
+     * the average, and normalizes to create asymmetry-like data. Works best
+     * for high fields (>few kGauss) where depolarization is minimal.
+     */
     virtual void DoLifeTimeCorrection(Double_t fudge);
 
+    /**
+     * \brief Returns metadata string for a specific data set.
+     * \param idx Data set index
+     * \return Metadata string, or empty string if idx out of range
+     */
     TString GetInfo(const UInt_t idx);
+
+    /**
+     * \brief Returns data set tag identifier.
+     * \param idx Data set index
+     * \return Data set tag, or -1 if idx out of range
+     */
     Int_t GetDataSetTag(const UInt_t idx);
+
+    /**
+     * \brief Returns number of stored data sets.
+     * \return Number of data sets added via AddData()
+     */
     UInt_t GetNoOfData() { return fRawData.size(); }
+
+    /**
+     * \brief Creates ROOT histograms for all processed data sets.
+     * \return Vector of TH1F pointers (caller owns the histograms)
+     *
+     * Creates histograms with proper time binning, respecting time ranges
+     * and packing. The caller is responsible for deleting the histograms.
+     */
     std::vector<TH1F*> GetData();
+
+    /**
+     * \brief Creates ROOT histogram for a specific processed data set.
+     * \param idx Data set index
+     * \return TH1F pointer (caller owns), or nullptr if idx out of range
+     *
+     * Creates a histogram with proper time binning for the specified data set.
+     * The caller is responsible for deleting the histogram.
+     */
     TH1F *GetData(const UInt_t idx);
 
   private:
-    std::vector<musrFT_data> fRawData;
-    std::vector<PDoubleVector>fData;
-    Int_t fBkgRange[2];
-    PDoubleVector fBkg;
-    Int_t fPacking;
+    std::vector<musrFT_data> fRawData;  ///< Raw input data sets with metadata
+    std::vector<PDoubleVector> fData;   ///< Processed data (after t0, corrections, packing)
+    Int_t fBkgRange[2];                 ///< Background range: [0]=start bin, [1]=end bin (-1=unused)
+    PDoubleVector fBkg;                 ///< Explicit background values (one per data set)
+    Int_t fPacking;                     ///< Rebinning factor (1=no rebinning, N=combine N bins)
 
+    /**
+     * \brief Initializes processed data from raw data.
+     *
+     * Copies raw data to fData starting from t0 bin. This is called
+     * automatically by processing methods if needed.
+     */
     virtual void InitData();
 };