items                 package:memisc                 R Documentation

_S_u_r_v_e_y _I_t_e_m_s

_D_e_s_c_r_i_p_t_i_o_n:

     Objects of class 'item' are data vectors with additional
     information attached to them like ``value labels'' and
     ``user-defined missing values'' known from software packages like
     SPSS or Stata.

_U_s_a_g_e:

     ## The constructor for objects of class "item"
     ## more convenient than new("item",...)
     ## S4 method for signature 'numeric':
     as.item(x,
       labels=NULL,  missing.values=NULL,
       valid.values=NULL,  valid.range=NULL,
       value.filter=NULL,  measurement=NULL,
       annotation=attr(x,"annotation"), ...
       )
     ## S4 method for signature 'character':
     as.item(x,
       labels=NULL,  missing.values=NULL,
       valid.values=NULL,  valid.range=NULL,
       value.filter=NULL,  measurement=NULL,
       annotation=attr(x,"annotation"), ...
       )

     ## S4 method for signature 'logical':
     as.item(x,...)
     # x is first coerced to integer,
     # arguments in ... are then passed to the "numeric"
     # method.

     ## S4 method for signature 'factor':
     as.item(x,...)
     ## S4 method for signature 'ordered':
     as.item(x,...)

     ## S4 method for signature 'double.item':
     as.item(x,
       labels=NULL,  missing.values=NULL,
       valid.values=NULL,  valid.range=NULL,
       value.filter=NULL,  measurement=NULL,
       annotation=attr(x,"annotation"), ...
       )

     ## S4 method for signature 'integer.item':
     as.item(x,
       labels=NULL,  missing.values=NULL,
       valid.values=NULL,  valid.range=NULL,
       value.filter=NULL,  measurement=NULL,
       annotation=attr(x,"annotation"), ...
       )

     ## S4 method for signature 'character.item':
     as.item(x,
       labels=NULL,  missing.values=NULL,
       valid.values=NULL,  valid.range=NULL,
       value.filter=NULL,  measurement=NULL,
       annotation=attr(x,"annotation"), ...
       )

_A_r_g_u_m_e_n_t_s:

       x: for 'as.item' methods, any atomic vector; for the
          'as.character', 'as.factor', 'as.integer', 'as.double', a
          vector with class '"item"'; for the 'unique',  'summary',
          'str', 'print', '[', and '<-' methods, a vector with class
          'labelled'. 

  labels: a named vector of the same mode as 'x'.

missing.values: either a vector of the same mode as 'x', or a list with
          components '"values"', vector of the same mode as 'x' (which
          defines individual missing values) and '"range"' a matrix
          with two rows with the same mode as 'x' (which defines a
          range of missing values), or an object of class
          '"missing.values"'. 

valid.values: either a vector of the same mode as 'x', defining those
          values of 'x' that are to be considered as valid, or an
          object of class '"valid.values"'.

valid.range: either a vector of the same mode as 'x' and length 2,
          defining a range of valid values of 'x', or an object of
          class '"valid.range"'.

value.filter: an object of class '"value.filter"', that is, of classes
          '"missing.values"', '"valid.values"', or '"valid.range"'.

measurement: level of measurement; one of "nominal", "ordinal",
          "interval", or "ratio".

annotation: a named character vector, or an object of class
          '"annotation"' 

     ...: further arguments, ignored.

_S_e_e _A_l_s_o:

     'annotation' 'labels' 'value.filter'

_E_x_a_m_p_l_e_s:

       x <- as.item(rep(1:5,4),
           labels=c(
               "First"      = 1,
               "Second"     = 2,
               "Third"      = 3,
               "Fourth"     = 4,
               "Don't know" = 5
             ),
           missing.values=5,
           annotation = c(
             description="test"
           ))
       str(x)
       summary(x)
       as.numeric(x)

       test <- as.item(rep(1:6,2),labels=structure(1:6,
                                           names=letters[1:6]))
       test
       test == 1
       test != 1
       test == "a"
       test != "a"
       test == c("a","z")
       test != c("a","z")
       test 
       test 

       codebook(test)

       Test <- as.item(rep(letters[1:6],2),
                         labels=structure(letters[1:6],
                                          names=LETTERS[1:6]))
       Test
       Test == "a"
       Test != "a"
       Test == "A"
       Test != "A"
       Test == c("a","z")
       Test != c("a","z")
       Test 
       Test 

       as.factor(test)
       as.factor(Test)
       as.numeric(test)
       as.character(test)
       as.character(Test)

       as.data.frame(test)[[1]]

