Standard classification algorithms cannot be directly applied to
raw time-series accelerometer data. Instead, we first must transform
the raw time series data into examples [18]. To accomplish
this we divided the data into 10-second segments and then generated
features that were based on the 200 readings contained
within each 10-second segment. We refer to the duration of each
segment as the example duration (ED). We chose a 10-second ED
because we felt that it provided sufficient time to capture several
repetitions of the (repetitive) motions involved in some of the six
activities. Although we have not performed experiments to determine
the optimal example duration value, we did compare the
results for a 10-second and 20-second ED and the 10-second ED
yielded slightly better results (as well as twice as many training
examples).