Computes distance matrices among the samples of two or more multivariate time-series.

Computes distance matrices among the samples of two or more multivariate time-series provided in a single dataframe (generally produced by prepareSequences), identified by a grouping column (argument grouping.column). Distances can be computed with the methods "manhattan", "euclidean", "chi", and "hellinger", and are implemented in the function distance. The function uses the packages parallel, foreach, and doParallel to compute distances matrices among different sequences in parallel. It is configured to use all processors available minus one.

distanceMatrix(
  sequences = NULL,
  grouping.column = NULL,
  time.column = NULL,
  exclude.columns = NULL,
  method = "manhattan",
  parallel.execution = TRUE
  )

Arguments

sequences

dataframe with multiple sequences identified by a grouping column. Generally the ouput of prepareSequences.

grouping.column

character string, name of the column in sequences to be used to identify separates sequences within the file. This argument is ignored if sequence.A and sequence.B are provided.

time.column

character string, name of the column with time/depth/rank data. The data in this column is not modified.

exclude.columns

character string or character vector with column names in sequences, or squence.A and sequence.B to be excluded from the analysis.

method

character string naming a distance metric. Valid entries are: "manhattan", "euclidean", "chi", and "hellinger". Invalid entries will throw an error.

parallel.execution

boolean, if TRUE (default), execution is parallelized, and serialized if FALSE.

Value

A list with named slots containing the the distance matrices of every possible combination of sequences according to grouping.column.

Details

Distances are computed as:

  • manhattan: d <- sum(abs(x - y))

  • euclidean: d <- sqrt(sum((x - y)^2))

  • chi: xy <- x + y y. <- y / sum(y) x. <- x / sum(x) d <- sqrt(sum(((x. - y.)^2) / (xy / sum(xy))))

  • hellinger: d <- sqrt(1/2 * sum(sqrt(x) - sqrt(y))^2)

Note that zeroes are replaced by 0.00001 whem method equals "chi" or "hellinger".

See also

distance

Author

Blas Benito <blasbenito@gmail.com>

Examples


#loading data
data(sequenceA)
data(sequenceB)

#preparing datasets
AB.sequences <- prepareSequences(
 sequence.A = sequenceA,
 sequence.A.name = "A",
 sequence.B = sequenceB,
 sequence.B.name = "B",
 merge.mode = "complete",
 if.empty.cases = "zero",
 transformation = "hellinger"
 )

#computing distance matrix
AB.distance.matrix <- distanceMatrix(
 sequences = AB.sequences,
 grouping.column = "id",
 method = "manhattan",
 parallel.execution = FALSE
 )


#plot
if(interactive()){
 plotMatrix(distance.matrix = AB.distance.matrix)
}