sieve {vcd} | R Documentation

## Extended Sieve Plots

### Description

(Extended) sieve displays for n-way contingency tables: plots rectangles with areas proportional to the expected cell frequencies and filled with a number of squares equal to the observed frequencies. Thus, the densities visualize the deviations of the observed from the expected values.

### Usage

    ## Default S3 method:
    sieve(x, condvars = NULL, gp = NULL, shade = NULL,
      legend = FALSE, split_vertical = NULL, direction = NULL, spacing = NULL,
      spacing_args = list(), sievetype = c("observed","expected"),
      main = NULL, sub = NULL, ...)
    ## S3 method for class 'formula':
    sieve(formula, data, ..., main = NULL, sub = NULL, subset = NULL)

### Arguments

`x` | a contingency table in array form, with optional category labels specified in the `dimnames(x)` attribute.
`condvars` | vector of integers or character strings indicating conditioning variables, if any. The table will be permuted to order them first.
`formula` | a formula specifying the variables used to create a contingency table from `data`. For convenience, conditioning formulas can be specified; the conditioning variables will then be used first for splitting. Formulas for sieve displays (unlike those for doubledecker plots) have no response variable.
`data` | either a data frame, or an object of class `"table"` or `"ftable"`.
`subset` | an optional vector specifying a subset of observations to be used.
`shade` | logical specifying whether `gp` should be used or not (see `gp`). If `TRUE` and `expected` is unspecified, a default model is fitted: if `condvars` is specified, a corresponding conditional independence model, and else the total independence model. If `shade` is `NULL` (default), `gp` is used if specified.
`sievetype` | logical indicating whether rectangles should be filled according to `observed` or `expected` frequencies.
`gp` | object of class `"gpar"`, shading function or a corresponding generating function (see details of `strucplot` and `shadings`). Components of `"gpar"` objects are recycled as needed along the last splitting dimension. The default is a modified version of `shading_Friendly`: if `sievetype` is `"observed"`, cells with positive residuals are painted red, and cells with negative residuals blue. If `sievetype` is `"expected"`, the sieves' color is gray. Ignored if `shade = FALSE`.
`legend` | either a legend-generating function, a legend function (see details of `strucplot` and `legends`), or a logical value. If `legend` is `NULL` or `TRUE` and `gp` is a function, legend defaults to `legend_resbased`.
`split_vertical` | vector of logicals of length k, where k is the number of margins of `x` (default: `FALSE`). Values are recycled as needed. A `TRUE` component indicates that the tile(s) of the corresponding dimension should be split vertically, `FALSE` means horizontal splits. Ignored if `direction` is not `NULL`.
`direction` | character vector of length k, where k is the number of margins of `x` (values are recycled as needed). For each component, a value of `"h"` indicates that the tile(s) of the corresponding dimension should be split horizontally, whereas `"v"` indicates vertical split(s).
`spacing` | spacing object, spacing function, or corresponding generating function (see `strucplot` for more information). The default is `spacing_equal` if `x` has two dimensions, and `spacing_increase` for more dimensions.
`spacing_args` | list of arguments for the generating function, if specified (see `strucplot` for more information).
`main, sub` | either a logical, or a character string used for plotting the main (sub) title. If logical and `TRUE`, the name of the `data` object is used.
`...` | Other arguments passed to `strucplot`

### Details

`sieve` is a generic function which currently has a default method and a formula interface. Both are high-level interfaces to the `strucplot` function, and produce (extended) sieve displays. Most of the functionality is described there, such as specification of the independence model, labeling, legend, spacing, shading, and other graphical parameters.

The layout is very flexible: the specification of shading, labeling, spacing, and legend is modularized (see `strucplot` for details).

### Value

The `"structable"` visualized is returned invisibly.

### Author(s)

David Meyer David.Meyer@R-project.org

### References

H. Riedwyl & M. Schüpbach (1994), Parquet diagram to plot contingency tables. In F. Faulbaum (ed.), Softstat '93: Advances in Statistical Software, 293–299. Gustav Fischer, New York.

M. Friendly (2000), Visualizing Categorical Data, SAS Institute, Cary, NC.

### See Also

`assoc`, `strucplot`, `mosaic`, `structable`, `doubledecker`

### Examples

    data(HairEyeColor)

    ## aggregate over 'sex':
    (tab <- margin.table(HairEyeColor, c(2,1)))

    ## plot expected values:
    sieve(tab, sievetype = "expected", shade = TRUE)

    ## plot observed table:
    sieve(tab, shade = TRUE)

    ## plot complete diagram:
    sieve(HairEyeColor, shade = TRUE)

    ## an example for the formula interface:
    data(VisualAcuity)
    sieve(Freq ~ right + left,  data = VisualAcuity)

    ## example with observed values in the cells:
    sieve(Titanic, pop = FALSE, shade = TRUE)
    labeling_cells(text = Titanic, gp = gpar(fontface = 2))(Titanic)

[Package vcd version 0.9-6 Index]