Added a short description of the 'custom' sampling.

README.md

@@ -49,7 +49,7 @@ calculate_statistics(
 
     :param sampling: temporal aggregation, one of ``daily``,
                      ``monthly``, ``seasonal``, ``vegseason``,
-                     ``summer``, ``xsummer``, or ``annual``;
+                     ``summer``, ``xsummer``, ``annual``, or ``custom``;
                      ``summer`` will pick the 6-months summer season in
                      the hemisphere where the station is located;
                      ``xsummer`` does the same for a 7-months summer
@@ -57,7 +57,9 @@ calculate_statistics(
                      ``vegseason`` requires also the ``crops`` argument
                      and will then determine the appropriate growing
                      seasons based on the ``climatic_zone`` metadata and
-                     crop type
+                     crop type;
+                     ``custom`` will create one aggregate value over the
+                     entire time series
     :param statistics: a single statistic or metric or a list of
                        statistics and metrics to call, these must be
                        defined in ``stats.py`` or ``ozone_metrics.py``

toarstats/metrics/interface.py

@@ -34,7 +34,9 @@ def calculate_statistics(
                      ``vegseason`` requires also the ``crops`` argument
                      and will then determine the appropriate growing
                      seasons based on the ``climatic_zone`` metadata and
-                     crop type
+                     crop type;
+                     ``custom`` will create one aggregate value over the
+                     entire time series
     :param statistics: a single statistic or metric or a list of
                        statistics and metrics to call, these must be
                        defined in ``stats.py`` or ``ozone_metrics.py``