Visualizing Categorical Data: fourfold

The fourfold macro ( get fourfold.sas)

SAS/IML modules for four-fold display of 2 x 2 x k tables

Usage

proc iml;
   %include iml(fourfold);
  *-- specify required parameters;
   dim =    { ... };   *-- table dimensions;
   table  = { ... };   *-- contingency table;
   vnames = { ... };   *-- variable names;
   lnames = { ... };   *-- level names;
  *-- specify desired global variables;
   config = {1};
   run fourfold( dim, table, vnames, lnames );

Required parameters

dim

A numeric vector containing the dimensions of the contingency table. The first two elements must be {2 2}.

table

A numeric matrix containing dim[1]=2 columns and number of rows equal to the product of the remaining elements of dim. The table must be entered so that the first variable varies most quickly (row-major order), and the last variable varies most slowly, in accord with the conventions for multiway tables used by the SAS/IML routines marg and ipf.

vnames

A 1 x ncol(dim) character vector, containing the names of the variables in the order corresponding to dim.

lnames

A character matrix containing the names of the categories (levels) of the variables, whose rows correspond to dim and vnames. Any short rows must be filled in with blank character strings, because matrices in SAS/IML must have the same number of elements in each row. For example, for the 2 x 2 x 6 table for the Berkeley data, the dim, vnames and lnames may be entered as follows:

   dim = {2 2 6};
   vnames = {'Admit?' 'Sex' 'Department'};
   lnames = {'Yes' 'No' ' '  ' '  ' '  ' ',
             'Male'  'Female' ' '  ' '  ' '  ' ',
             'A' 'B' 'C' 'D' 'E' 'F'};

Global input variables

std

Specifies how the 2 x 2 tables are standardized. [Default: std='MARG'.

MARG

standardizes each 2 x 2 table to equal margins, keeping the odds ratio fixed. The config variable determines which margins are equated.

MAX

standardizes each table to a maximum cell frequency of 100. This has the effect of equating the totals in each table.

MAXALL

standardizes all tables so that the maximum cell entry is 100.

config

specifies the margins to standardize, when std='MARG'. config={1 2} equates both the row and column variable in each table; config={1} equates the margin only for the column variable in each table; config={2} equates only the row variable.

down

Specifies the number of fourfold panels down each page

across

Specifies the number of panels across each page

sangle

The angle for side labels (0 | 90). [Default: sangle=90].

colors

The names of two colors to use for the smaller and larger diagonals of each 2x2 table. The positions of first color indicate the direction of association. [Default: colors={BLUE RED}].

patterns

The names of two fill patterns. For grayscale, use patterns={SOLID SOLID} and colors={GRAYC0 GRAY80}. [Default: patterns={SOLID SOLID}].

alpha

is the error rate used for confidence rings on the odds ratios. Use alpha=0; to suppress the confidence rings.

conf

The type of confidence rings, either 'Individual' (for each 2 x 2 table) or 'Joint' (for simultaneous confidence intervals covering all k 2 x 2 tables). [Default: conf='Individual'].

font

A character string specifying the font used. The default is Helvetica (font='hwpsl009') if a PostScript driver is being used, SWISS otherwise.

frame

the line style for the boxed frame (0=none).

Example

proc iml;
   %include iml(fourfold.sas);
   *-- Berkeley Admissions data;
   dim = {2 2 6};
   vnames = {'Admit?' 'Sex' 'Department'};
   lnames = {'Yes' 'No' ' '  ' '  ' '  ' ',
             'Male'  'Female' ' '  ' '  ' '  ' ',
             'A' 'B' 'C' 'D' 'E' 'F'};
   table = { 512  313, 89   19,
             353  207, 17    8,
             120  205, 202  391,
             138  279, 131  244,
              53  138, 94  299,
              22  351, 24  317};
   std='MARG';  /* IML4FOLD, fig 3 */
   alpha=.01;
   patterns={solid solid};
   htext = 2.4;
   filltype={hls hls};
   run fourfold(dim, table, vnames, lnames);

See also