mvm {dtw}

Minimum Variance Matching algorithm

Description

Step patterns to compute the Minimum Variance Matching (MVM) correspondence between time series

Usage

mvmStepPattern(elasticity = 20)

Arguments

elasticity

integer: maximum consecutive reference elements skippable

Details

The Minimum Variance Matching algorithm (1) finds the non-contiguous parts of reference which best match the query, allowing for arbitrarily long "stretches" of reference to be excluded from the match. All elements of the query have to be matched. First and last elements of the query are anchored at the boundaries of the reference.

The mvmStepPattern function creates a stepPattern object which implements this behavior, to be used with the usual dtw() call (see example). MVM is computed as a special case of DTW, with a very large, asymmetric-like step pattern.

The elasticity argument limits the maximum run length of reference which can be skipped at once. If no limit is desired, set elasticity to an integer at least as large as the reference (computation time grows linearly).

Value

A step pattern object.

Author(s)

Toni Giorgino

References

Latecki, L. J.; Megalooikonomou, V.; Wang, Q. & Yu, D. An elastic partial shape matching technique Pattern Recognition, 2007, 40, 3069-3080. doi:10.1016/j.patcog.2007.03.004

See Also

Other objects in stepPattern().

Examples

## The hand-checkable example given in Fig. 5, ref. [1] above
diffmx <- matrix( byrow=TRUE, nrow=5, c(
  0,  1,  8,  2,  2,  4,  8,
  1,  0,  7,  1,  1,  3,  7,
 -7, -6,  1, -5, -5, -3,  1,
 -5, -4,  3, -3, -3, -1,  3,
 -7, -6,  1, -5, -5, -3,  1 ) ) ;

## Cost matrix
costmx <- diffmx^2;

## Compute the alignment
al <- dtw(costmx,step.pattern=mvmStepPattern(10))

## Elements 4,5 are skipped
print(al$index2)

plot(al,main="Minimum Variance Matching alignment")