Also,
I already have a column that records the minute each measurement is made, there being 4 measurements taken each second (4 * 60 = 240 measurements a minute). So I'm thinking that I might be able to construct a loop that looks to see if the minute column has changed (say, from minute 0 to minute 1) and if so, average/take variance of the values stored in some temporary variable...
Am I on the right track?