The invention concerns a method of processing data to provide output data based on a group of data samples having a time stamp falling within at least one rolling time period, the method comprising: receiving a new data sample and associating said new data sample with a first time stamp; updating said output data corresponding to a first rolling time period to be based on said group of data samples including said new data sample; programming a first callback based on said first time stamp and on the duration of said first rolling time period; and in response to the occurrence of said first callback, updating said output data corresponding to said first rolling time period to no longer be based on said new data sample.