\name{dtwWindowingFunctions}
\alias{noWindow}
\alias{sakoeChibaWindow}
\alias{slantedBandWindow}
\alias{itakuraWindow}
\alias{dtwWindowingFunctions}
\alias{dtwWindow.plot}



\title{Global constraints and windowing functions for DTW}
\description{
  Various global constraints (windows) which can be applied to
  the \code{window.type} argument of \code{\link{dtw}},
  including the Sakoe-Chiba band, the Itakura parallelogram,
  and custom functions.
}

\usage{
noWindow(iw, jw, ...);
sakoeChibaWindow(iw,jw,  window.size,...);
slantedBandWindow(iw,jw,query.size,template.size,  window.size,...);
itakuraWindow(iw,jw,query.size,template.size,  ...); 

dtwWindow.plot(fun,query.size=200,template.size=220,...);

}
%- maybe also 'usage' for other objects documented here.
\arguments{
  \item{iw}{ index in the query (row) -- automatically set }
  \item{jw}{ index in the template (column) -- automatically set }
  \item{query.size}{ size of the query time series -- automatically set }
  \item{template.size}{ size of the template time series -- automatically set }
  \item{window.size}{ window size, used by some windowing functions -- must be set}
  \item{fun}{ a windowing function }
  \item{...}{additional arguments passed to windowing functions}
}
\details{

  Windowing functions can be passed to the
  \code{window.type} argument in \code{\link{dtw}} to put a global
  constraint to the warping paths allowed. They take two integer
  arguments (plus optional parameters) and must return a boolean value 
  \code{TRUE} if the coordinates fall within the allowed region 
  for warping paths, \code{FALSE} otherwise.

  \code{dtwWindow.plot} can be used to visualize a chosen windowing 
  function. Some functions take parameters which must be set (e.g. 
  window.size). \code{dtwWindow.plot}  plots a 200 x 220  rectangular
  region by default, which can be changed passing \code{template.size} 
  and  \code{query.size} arguments.
  
  User-defined functions can read variables \code{template.size},
  \code{query.size} and \code{window.size}; these are pre-set upon invocation.
  User-defined functions are free to implement any window
  shape, as long as at least one path is allowed between the initial and
  final alignment points, i.e., they are compatible with the DTW
  constraints.

  The Sakoe-Chiba band is a band of \code{window.size} elements
  around the main diagonal. If the window size is too small, i.e. 
  $\code{template.size}-\code{query.size}
  > \code{window.size}$,  warping becomes
  impossible.

  A widely held misconception is that the "Itakura parallelogram" 
  (as described in reference [2]) is a \emph{global} constraint, i.e. a window.
  To the author's knowledge, it instead arises from the local slope restrictions imposed to 
	the warping path (they are implemented in this
  package through the \code{\link{asymmetricItakura}} step pattern. 

  An \code{itakuraWindow}  global constraint is still provided with this
  package.    See example below for a demonstration of
  the difference between a local the two.

  The \code{slantedBandWindow} is a package-specific window: it is a
  band centered around the (jagged) line segment
  which joins element \code{[1,1]} to element
  \code{[query.size,template.size]}, and will be
  \code{window.size} columns wide.

}

\note{
  Although  \code{dtwWindow.plot} resembles object-oriented notation,
  there is not a such a dtwWindow class currently.
}

\value{
  Windowing functions return \code{TRUE} if the coordinates passed as
  arguments fall within the chosen warping window, \code{FALSE}
  otherwise. User-defined functions should do the same.
}

\references{ 
[1] Sakoe, H.; Chiba, S., \emph{Dynamic programming algorithm optimization for spoken word recognition,}
 Acoustics, Speech, and Signal Processing [see also IEEE Transactions on Signal Processing], IEEE Transactions on , 
vol.26, no.1, pp. 43-49, Feb 1978 URL: \url{http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1163055} \cr
\cr
[2] Itakura, F., \emph{Minimum prediction residual principle applied to speech
recognition,} Acoustics, Speech, and Signal Processing [see also IEEE
Transactions on Signal Processing], IEEE Transactions on , vol.23, no.1, pp.
67-72, Feb 1975. URL: \url{http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1162641} 

}


\author{Toni Giorgino}

\examples{

## Display some windowing functions
dtwWindow.plot(itakuraWindow, main="So-called Itakura parallelogram window")
dtwWindow.plot(slantedBandWindow, window.size=2,
  template=13, query=17, main="The slantedBandWindow at window.size=2")


## Asymmetric step with Sakoe-Chiba band

idx<-seq(0,6.28,len=100); 
query<-sin(idx)+runif(100)/10;
template<-cos(idx);

asyband<-dtw(query,template,keep=TRUE,
             step=asymmetric,
             window.type=sakoeChibaWindow,
             window.size=30                  );

dtwPlot(asyband,type="density",main="Sine/cosine: asymmetric step, S-C window")


}


\concept{Dynamic Time Warp}
\concept{Global contraint}
\concept{Windowing}
\concept{Sakoe-Chiba Band}
\concept{Itakura Parallelogram}


\keyword{ ts }