derivative.rb in gphys-1.4.3

- old
+ new

@@ -11,10 +11,12 @@
 * ((<module NumRu::GPhys::Derivative>))
   * ((<threepoint_O2nd_deriv>))
     * First derivative (2nd Order difference use three point.)
   * ((<cderiv>))
     * First derivative (using center difference method)
+  * ((<deriv2d>))
+    * 2nd derivative
 
 =module NumRu::GPhys::Derivative
 
 Module functions of Derivative Operater for GPhys.
 
@@ -67,9 +69,18 @@
       -- conveneient to make deribative in a different cooridate scaling.
       (e.g., differenciate in radian, while the coordinate is in degrees)
 
     RETURN VALUE
     * a GPhys
+
+---deriv2nd(gp, dim_or_dimname, bc=LINEAR_EXT, altcoord=nil)
+
+    2nd Derivate (({gp})) respect to (({dim})) th or (({dimname})) dimension 
+    covering non-uniform grids. Based on:
+      ( (z_{i+1}-z_{i})/(x_{i+1}-x_{i}) - (z_{i}-z_{i-1})/(x_{i}-x_{i-1}) )
+      / ((x_{i+1}-x_{i-1})/2)
+
+    See ((<cderiv>)) for usage.
 
 =end
 ############################################################
 
 module NumRu