drop                  package:base                  R Documentation

Drop Redundant Extent Information

Description:

     Delete the dimensions of an array which have only one level.

Usage:

     drop(x)

Arguments:

       x: an array (including a matrix).

Value:

     If 'x' is an object with a 'dim' attribute (e.g., a matrix or
     'array'), then 'drop' returns an object like 'x', but with any
     extents of length one removed.  Any accompanying 'dimnames'
     attribute is adjusted and returned with 'x': if the result is a
     vector the 'names' are taken from the 'dimnames' (if any).  If the
     result is a length-one vector, the names are taken from the first
     dimension with a dimname.

     Array subsetting ('[') performs this reduction unless used with
     'drop = FALSE', but sometimes it is useful to invoke 'drop'
     directly.

See Also:

     'drop1' which is used for dropping terms in models.

Examples:

     dim(drop(array(1:12, dim=c(1,3,1,1,2,1,2))))# = 3 2 2
     drop(1:3 %*% 2:4)# scalar product

