seqST {TraMineR} | R Documentation |
Computes the turbulence for each sequence in a sequence data set, using the measure proposed by Elzinga.
seqST(seqdata)
seqdata |
a sequence object as returned by the the seqdef function. |
Sequence turbulence is a measure proposed by Elzinga (2007). It is based on the number phi(x) of distinct subsequences that can be extracted from the distinct state sequence and the variance of the consecutive times t_i spent in the distinct states. For a sequence x, the formula is
T(x)=log_{2}(phi(x),frac{s_{t,max}^{2}(x)+1}{s_{t}(x)+1})
where s_{t} is the variance of the state-duration for the x sequence and s_{t,max} is the maximum value that this variance can take given the total duration of the sequence. This maximum is computed as follow
s_{t,max}=(n-1)(1-bar{t})
where bar t is the mean consecutive time spent in the distinct states, i.e. the sequence duration divided by the number of distinct states in the sequence.
a vector whose number of elements is the number of sequences in seqdata
, containing the turbulence value of each sequence.
Elzinga, Cees H. and Liefbroer, Aart C. (2007). De-standardization of Family-Life Trajectories of Young Adults: A Cross-National Comparison Using Sequence Analysis. European Journal of Population, 23, 225-250.
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## Loading the 'actcal' example data set data(actcal) ## Defining a sequence object with data in columns 13 to 24 ## (activity status from january to december 2000) actcal.seq <- seqdef(actcal,13:24, informat='STS') ## Computing the sequences turbulence turb <- seqST(actcal.seq) ## Histogram for the turbulence hist(turb)