Calculating average speed

D'Arcy Norman has a Computed Field example in which he calculates the average speed of a bike trip, rather than filling it in manually:

Computed Field settings (leaving other fields at their defaults):

• Computed Code:$node_field[0]['value'] = ($node->field_distance[0]['value'] / $node->field_duration[0]['value']) * 60;
• Check 'Store using the database settings below
• Data Type: float
• Data Length: 10,2
• Default Value: 0
• Check 'Sortable' to make the field sortable in views.

The end result can then be displayed in a sortable view.