Find beginning and end of a series of events

Hi I have a log file that captures events with a timestamp. When no event occurs nothing is logged, meaning there is no continuous time stamp data. My goal is to identify when each "usage session" starts and ends based on some criterion: e.g. no event occurred for x hours. Is there an easy way to identify start/end through matlab?

Example data set (1st col: timestamp, 2nd/3rd: event)

    [   59.2945]    '00070051'    'Down'  
    [   59.4056]    '00070051'    'Down'  
    [   59.6964]    '00070051'    'Down'  
    [   59.8762]    '00070051'    'Down'  
    [   59.9439]    '00070051'    'Down'  
    [   60.0577]    '00070051'    'Down'  
    [   61.0465]    '00070051'    'Down'  
    [   61.1140]    '00070051'    'Down'  
    [   61.2269]    '00070051'    'Down'  
    [   61.3165]    '00070051'    'Down'  
    [   61.4064]    '00070051'    'Down'  
    [   61.5191]    '00070051'    'Down'  
    [   61.6088]    '00070051'    'Down'  
    [   61.7668]    '00070051'    'Down'  
    [   61.8563]    '00070051'    'Down'  
    [   61.9915]    '00070051'    'Down'  
    [   62.1038]    '00070051'    'Down'  
    [   62.2181]    '00070051'    'Down'  
    [   62.3292]    '00070051'    'Down'  
    [   62.4416]    '00070051'    'Down'  
    [   62.5540]    '00070051'    'Down'  
    [   62.6663]    '00070051'    'Down'  
    [   62.7564]    '00070051'    'Down'  
    [   62.8914]    '00070051'    'Down'  
    [  135.5951]    '000c0223'    'Home'  
    [  135.7017]    '000c0223'    'Home'  
    [  142.2507]    '0007004f'    'Right' 
    [  142.3606]    '0007004f'    'Right' 
    [  142.4056]    '0007004f'    'Right' 
    [  142.5180]    '0007004f'    'Right' 
    [  142.5855]    '0007004f'    'Right' 
    [  142.6978]    '0007004f'    'Right' 
    [  142.7430]    '0007004f'    'Right' 
    [  142.8557]    '0007004f'    'Right' 
    [  142.9018]    '0007004f'    'Right' 
    [  143.0128]    '0007004f'    'Right' 
    [  143.1928]    '00070058'    'Select'
    [  143.3054]    '00070058'    'Select'
    [  144.4978]    '00070051'    'Down'  
    [  144.5890]    '00070051'    'Down'  
    [  144.7921]    '0007004f'    'Right' 
    [  144.9256]    '0007004f'    'Right' 
    [  144.9704]    '0007004f'    'Right' 
    [  145.1065]    '0007004f'    'Right'

Answer 1

[Benjamin Kraus]

My first thought is to use diff on the timestamps (to get the time between events) and then threshold the results (anything over a certain time is the start of a new session).

How long are the gaps between each session relative to the inner-event interval within a session?

[TF_SF]

Hi Benjamin, Thank you for the suggestion. I am using your proposed approach. The time difference between each session is magnitudes higher than between individual events, so it should be easy implement a simple threshold. Thanks!