libpsdxx [WP]: declaration of functions for logarithmic sampling

src/libs/libpsdxx/psd.h

@@ -124,6 +124,11 @@ namespace psd {
 
   /* ====================================================================== */
 
+  //! series container (for frequency values, for example)
+  typedef aff::Series<double> TDseries;
+
+  /* ====================================================================== */
+
   //! return absolute value (magnitude) of complex values
   TDISeries abs(const TDCISeries::Tcoc& s);
 
@@ -204,16 +209,32 @@ namespace psd {
 
   /* ====================================================================== */
 
-  /*! \brief support sampling in the frequency domain
-   *
-   * This class supports logarithmic sampling and averaging in the frequency
-   * domain.
-   *
-   * Samples data which is provided on a uniformly spaced frequency axis with
-   * an equal amount of samples per decade and performs averarging.
-   *
-   * Implemented as a function
-   */
+   /*! return a logarithmic frequency scale
+    *
+    * \param df sampling interval in Hz of uniformly samples spectral values
+    * \param nsamples number of samples of spectral data
+    * \param n_per_decade number of samples per frequency decade
+    *                     for logarithmic sampling
+    * \return series of frequency values in Hz with logarithmic spacing and 
+    *         \p n_per_decade frequency values per decade
+    *
+    * This function is used to compute a series of frequency values with
+    * logarithmic spacing. The return value can be used as input parameter to
+    * the actual sampling functions.
+    */
+  TDseries log_frequency(const double& df, 
+                         unsigned int& nsamples,
+                         unsigned int& n_per_decade);
+
+   /*! sample values on a logarithmic frequency axis
+    */
+   TDCISeries::Tseries log_sampling(const TDCISeries::Tcoc& s,
+                                    const TDseries::Tcoc& f);
+
+   /*! sample complex values on a logarithmic frequency axis
+    */
+   TDISeries::Tseries log_sampling(const TDISeries::Tcoc& s,
+                                   const TDseries::Tcoc& f);
 
 } // namespace psd