Added a member function to get the line intercept from running_gradient.

dlib/statistics/running_gradient.h

@@ -72,6 +72,18 @@ namespace dlib
             return w(0);
         }
 
+        double intercept (
+        ) const
+        {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(current_n() > 0,
+                "\t double running_gradient::intercept()"
+                << "\n\t You must add more values into this object before calling this function."
+                << "\n\t this: " << this
+                );
+
+            return w(1);
+        }
         double standard_error ( 
         ) const
         {

dlib/statistics/running_gradient_abstract.h

@@ -65,6 +65,19 @@ namespace dlib
                   of this line.
         !*/
 
+        double intercept (
+        ) const;
+        /*!
+            requires
+                - current_n() > 0
+            ensures
+                - This class fits a line to the time series data given to add().  This
+                  function returns the intercept of that line while gradient() returns the
+                  slope of that line.  This means that, for example, the next point that
+                  add() will see, as predicted by this best fit line, is the value
+                  intercept() + current_n()*gradient().
+        !*/
+
         double standard_error ( 
         ) const;
         /*!