Drupal Views has the option for grouping view results. But it can do much more. Beside grouping results, it can also get the total of each group. In Views, this is called Aggregation. For example, if you want the total production of each calendar week. The following data
Calendar Week Production 1 9227 1 8946 1 9492 2 9235 2 8944 2 9750 3 9221 3 8961 3 9878
will become
Calendar Week Production(Total) 1 27,665 2 27,929 3 28,060
Here is a video showing how to do it.