I am trying to do a comparison between documents in a MongoDB collection that has a time component. Let's assume the documents look like so:
{date: 2010-01-01, sales: 100}
{date: 2010-01-02, sales: 202}
{date: 2010-01-03, sales: 149}
Is it possible to lag the values for comparison? Is it possible to do some sort of running difference? Perhaps some projection allows for this result:
{date: 2010-01-01, sales: 100, previous_sales: Nan}
{date: 2010-01-02, sales: 202, previous_sales: 100}
{date: 2010-01-03, sales: 149, previous_sales: 202}