## A study of the "Itakura" parallelogram
##
## A widely held misconception is that the "Itakura parallelogram" (as
## described in the original article) is a global constraint. Instead,
## it arises from local slope restrictions. Anyway, an "itakuraWindow",
## is provided in this package. A comparison between the two follows.
## The local constraint: three sides of the parallelogram are seen
idx<-seq(0,6.28,len=100);
query<-sin(idx)+runif(100)/10;
reference<-cos(idx)
ita <- dtw(query,reference,keep=TRUE,step=typeIIIc)
dtwPlotDensity(ita, main="Slope-limited asymmetric step (Itakura)")
## Symmetric step with global parallelogram-shaped constraint. Note how
## long (>2 steps) horizontal stretches are allowed within the window.
dtw(query,reference,keep=TRUE,window=itakuraWindow)->ita;
dtwPlotDensity(ita,
main="Symmetric step with Itakura parallelogram window")
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