rely on centralised doc for flow transformation

include/evalhyd/evald.hpp

@@ -44,23 +44,9 @@ namespace evalhyd
     ///
     ///    transform: ``std::string``, optional
     ///       The transformation to apply to both streamflow observations and
-    ///       predictions prior to the calculation of the *metrics*. The options
-    ///       are listed in the table below.
+    ///       predictions prior to the calculation of the *metrics*.
     ///
-    ///       =========================  ==================================
-    ///       transformations            details
-    ///       =========================  ==================================
-    ///       ``"sqrt"``                 The square root function
-    ///                                  **f(Q) = √Q** is applied.
-    ///       ``"pow"``                  The power function
-    ///                                  **f(Q) = Qⁿ** is applied (where
-    ///                                  the power **n** can be set through 
-    ///                                  the *exponent* parameter).
-    ///       ``"inv"``                  The reciprocal function
-    ///                                  **f(Q) = 1/Q** is applied.
-    ///       ``"log"``                  The natural logarithm function
-    ///                                  **f(Q) = ln(Q)** is applied.
-    ///       =========================  ==================================
+    ///       .. seealso:: :doc:`../../functionalities/transformation`
     ///
     ///    exponent: ``double``, optional
     ///       The value of the exponent n to use when the *transform* is the