def process_data(MSD_list, TRACE_COUNT):
    trace_data = [{} for x in range(TRACE_COUNT)]
    for distance, delta_t, trace_id in MSD_list:
        if delta_t in trace_data[trace_id]:
            trace_data[trace_id][delta_t][0] += distance
            trace_data[trace_id][delta_t][1] += 1
        else:
            trace_data[trace_id][delta_t] = [distance, 1]

    MSD_traces = [[] for x in range(TRACE_COUNT)]

    for trace_id in range(TRACE_COUNT):
        for delta_t,v in sorted(trace_data[trace_id].items()):
            mean = v[0] / float(v[1])
            MSD_traces[trace_id].append((mean, delta_t))

    return MSD_traces