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\alias{Ops,structure,structure-method}
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\alias{Ops,structure,structure-method}
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\alias{Ops,structure,array-method}
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\alias{Ops,structure,array-method}
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\alias{Ops,vector,structure-method}
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\alias{Ops,vector,structure-method}
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\alias{Ops,array,structure-method}
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\alias{Ops,array,structure-method}
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\alias{Ops,array,array-method}
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\alias{Ops,array,array-method}
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\alias{initialize,array-method}
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\alias{initialize,matrix-method}
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\alias{initialize,ts-method}
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\alias{show,ts-method}
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%
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%
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\description{
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\description{
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  The virtual class \code{structure} and classes that
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  The virtual class \code{structure} and classes that
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  extend it are formal classes analogous to S language structures such
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  extend it are formal classes analogous to S language structures such
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  as arrays and time-series.
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  as arrays and time-series.
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  arguments to the corresponding function, e.g., to function
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  arguments to the corresponding function, e.g., to function
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  \code{matrix()}.  There is no particular advantage over calling those
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  \code{matrix()}.  There is no particular advantage over calling those
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  functions directly, unless you are writing software designed to work
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  functions directly, unless you are writing software designed to work
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  for multiple classes, perhaps with the class name and the arguments
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  for multiple classes, perhaps with the class name and the arguments
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  passed in.
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  passed in.
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  Objects created from the classes \code{"matrix"} and \code{"array"} are unusual, to put
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  it mildly, and have been for some time.  Although they may appear to
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  be objects from these classes, they do not have the internal
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  structure of either an S3 or S4 class object.  In particular, they
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  have no \code{"class"} attribute and are not recognized as objects
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  with classes (that is, both \code{\link{is.object}} and
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  \code{\link{isS4}} will return \code{FALSE} for such objects).
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  That the objects still behave as if they came from the corresponding
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  class (most of the time, anyway) results from special code
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  recognizing such objects being built into the base code of \R.
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  For most purposes, treating the classes in the usual way will work,
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  fortunately.  One consequence of the special treatment is that these
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  two classes\emph{may} be used as the data part of an S4 class; for
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  example, you can get away with \code{contains = "matrix"} in a call
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  to \code{\link{setGeneric}} to create an S4 class that is a subclass
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  of \code{"matrix"}.  There is no guarantee that everything will work
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  perfectly, but a number of classes have been written in this form
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  successfully.
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  The class \code{"ts"}  is basically an S3 class
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  that has been registered with S4, using the
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  \code{\link{setOldClass}} mechanism.  Versions of \R through 2.7.0
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  treated this class as a pure S4 class, which was in principal a good
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  idea, but in practice did not allow subclasses to be defined and had
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  other intrinsic problems.  (For example, setting the
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  \code{"tsp"} parameters as a slot often fails because the built-in
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  implementation does not allow the slot to be temporarily
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  inconsistent with the length of the data. Also, the S4 class
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  prevented the correct specification of the S3 inheritance for class
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  \code{"mts"}.)
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  The current behavior (beginning with version 2.8.0 of \R) registers
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  \code{"ts"} as an S3 class, but also provides some methods that at
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  least partially support classes that contain \code{"ts"}.  The S3
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  inheritance of \code{"mts"} in package \code{stats} is also registered.
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}
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}
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\section{Extends}{
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\section{Extends}{
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  The specific classes all extend class \code{"structure"}, directly, and
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  The specific classes all extend class \code{"structure"}, directly, and
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  class \code{"vector"}, by class \code{"structure"}.
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  class \code{"vector"}, by class \code{"structure"}.
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}
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}
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      vector structures as in the reference.
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      vector structures as in the reference.
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    }
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    }
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  }
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  }
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}
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}
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\references{
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\references{
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 Chambers, John M. (2008)
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 \emph{Software for Data Analysis: Programming with R}
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  Springer.  (For the R version.)
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 Chambers, John M. (1998)
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 \emph{Programming with Data}
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 Springer (For the original S4 version.)
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  Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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  Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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  \emph{The New S Language}.
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  \emph{The New S Language}.
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  Wadsworth \& Brooks/Cole.
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  Wadsworth \& Brooks/Cole (for the original vector structures).
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}
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}
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\examples{
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\examples{
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showClass("structure")
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showClass("structure")
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## explore a bit :
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## explore a bit :