TraMineR (version 1.1)

seqST: Sequences turbulence

Description

Computes the turbulence for each sequence in a sequence data set, using the measure proposed by Elzinga.

Usage

seqST(seqdata)

Arguments

seqdata

a sequence object as returned by the the seqdef function.

Value

• a vector whose number of elements is the number of sequences in seqdata, containing the turbulence value of each sequence.

Details

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.

References

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.

See Also

.

Examples

## 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)