In Metric2D, the configuration input aggregate_z can be a mathtematical...

In Metric2D, the configuration input aggregate_z can be a mathtematical expression involving several database fields.

documentations/userguide/metric2d.rst

@@ -17,7 +17,8 @@ Configure the 2-dim metrics
    on the database field ``people.id``.
 
 A ``metric`` is the result of an *aggregation function* applied on the values
-of a given database field.
+of a given database field or on the values of a mathematical expression
+involving several database fields.
 
 A 2-dim metric is a table displaying one metric when records are
 aggregated by values for a given database fields along the *x* and *y* axis.
@@ -70,12 +71,21 @@ Filter conditions
 Aggregate
 ---------
 
-The group fields and the metric are defined in the ``Aggregate`` tab. The
-entries ``Group (x)``, ``Group(y)`` and ``Aggregate (z)`` are equal to the
-address of database field, virtual field, key of the ``history.data``
-dictionary or the pseudo field ``year``.
+The group fields and the metric are defined in the ``Aggregate`` tab:
 
-The entry ``metric (z)`` is the name of the  aggregation function. Possible
-values are: ``count``, ``max``, ``mean``, ``median``, ``min``, ``size``,
-``std``, ``sum``, *etc*. In fact, all the descriptive stats methods of the
-DataFrame_ class.
\ No newline at end of file
+
+    ``Group (x)`` and ``Group(y)``
+        are equal to the address of database field, virtual field, key
+        of the ``history.data`` dictionary or the pseudo field ``year``.
+
+    ``Aggregate (z)``
+        is equal to the address of database field, virtual field, key
+        of the ``history.data`` dictionary or the pseudo field ``year``.
+        It can also be equal to a *mathematical expression* involving several
+        database fields.
+
+    ``metric (z)``
+        is equal to the name of the  aggregation function. Possible
+        values are: ``count``, ``max``, ``mean``, ``median``, ``min``, ``size``,
+        ``std``, ``sum``, *etc*. In fact, all the descriptive stats methods of
+        the DataFrame_ class.
\ No newline at end of file

modules/report_objects.py

@@ -15,6 +15,10 @@ from plugin_dbui import get_id, Store
 from StringIO import StringIO
 
 
+REG_DBFIELD = re.compile("\w+\.\w+(?:\.\w+)?", re.UNICODE)
+REG_SINGLE_DBFIELD = re.compile("^ *\w+\.\w+(\.\w+)? *$", re.UNICODE)
+
+
 def do_title(config, selector):
     """Build the report title.
     
@@ -938,6 +942,27 @@ class Metric2D(BaseReport):
         metric = {}
         metric[address_z] = aggregate 
         
+        # database field expression along the z axis
+        expression = None
+        if not REG_SINGLE_DBFIELD.match(address_z):
+            expression = address_z
+            ref_addresses = list(addresses)
+            
+            del maps[2]
+            del addresses[2]
+            
+            i = 0
+            for m in REG_DBFIELD.finditer(address_z):
+                address = m.group()
+                map = split_dbfield(address)
+                tmp = "a%i" % i
+                i += 1
+                
+                addresses.append(tmp)
+                maps.append(map)
+
+                expression = expression.replace(address, tmp)
+                
         # build the data frame
         data = self._do_data(maps)
         if not data:
@@ -946,6 +971,11 @@ class Metric2D(BaseReport):
         
         df = pd.DataFrame(data, columns=addresses)
         
+        # compute the expression and remove temporarely column
+        if expression:
+            df[address_z] = df.eval(expression)
+            df = df[ref_addresses]
+            
         # remove duplicate entries
         if aggregate in ('count', 'size'):
             df = df.drop_duplicates()