{smcl} {* 12may2003/20jan2009/21jan2009}{...} {hline} help for {hi:domdiag} {hline} {title:Dominance diagram} {p 8 17 2} {cmd:domdiag} {it:varname} [{cmd:if} {it:exp}] [{cmd:in} {it:range}] {cmd:, by(}{it:byvar}{cmd:)} [ {cmdab:rev:erse} {it:graph_options} ] {title:Description} {p 4 4 2}{cmd:domdiag} plots a dominance diagram given a division of the values of the numeric variable {it:varname} into precisely two groups by the categories of {it:byvar}. {p 4 4 2}Suppose there are {it:n_1} values in the group for the lower value of {it:varname} (hereafter called group 1) and {it:n_2} values in the group for the higher value of {it:varname} (group 2). Then there are {it:n_1} * {it:n_2} pairwise comparisons, which are plotted on a graph with axes rank on {it:varname} within group 1 and rank on {it:varname} within group 2. The symbols used are {cmd:"+"} if value in group 1 > value in group 2, {cmd:"0"} if value in group 1 = value in group 2, and {cmd:"-"} if value in group 1 < value in group 2. This helps to make graphic what is done in {cmd:ranksum}: the proportion of pairs symbolised {cmd:"+"} plus 1/2 the proportion of pairs symbolised {cmd:"0"} is the estimate that {bind:{it:P}(({it:varname} | group 1) > ({it:varname} | group 2))}. {p 4 4 2}By default, ranks for the group with fewer values are plotted on the {it:y} axis. {title:Remarks} {p 4 4 2}This graph was used by Cliff (1993, 1996). Some earlier related ideas are reviewed by Fisher (1983). Newson (2002) gives a broader discussion and an example implementing {cmd:domdiag}. {p 4 4 2}{cmd:domdiag} temporarily makes a dataset of {it:n_1} * {it:n_2} observations. This may be very much larger than the existing dataset and the user should make sure that enough memory is allocated. {title:Options} {p 4 8 2}{cmd:by(}{it:byvar}{cmd:}) specifies subdivision into two groups and is a required option. If {it:byvar} defines three or more categories and it is desired to focus on just two, make sure the others are excluded by using {cmd:if}. {p 4 8 2}{cmd:reverse} specifies that axes are to be reversed from the default. {p 4 8 2}{it:graph_options} are options of {help scatter}. By default, {cmd:note()} is used to display {it:P}(({it:varname} | group 1) > ({it:varname} | group 2)). {title:Examples} {p 4 8 2}{cmd:. domdiag mpg, by(foreign)} {title:Author} {p 4 4 2}Nicholas J. Cox, Durham University, U.K.{break} n.j.cox@durham.ac.uk {title:References} {p 4 8 2}Cliff, N. 1993. Dominance statistics: ordinal analyses to answer ordinal questions. {it:Psychological Bulletin} 114, 494{c -}509. {p 4 8 2}Cliff, N. 1996. {it:Ordinal methods for behavioral data analysis.} Mahwah, NJ: Lawrence Erlbaum. {p 4 8 2}Fisher, N.I. 1983. Graphical methods in nonparametric statistics: a review and annotated bibliography. {it:International Statistical Review} 51, 25{c -}38. {p 4 8 2}Newson, R. 2002. Parameters behind "nonparametric" statistics: Kendall's tau, Somers' D and median differences. {it:Stata Journal} 2: 45{c -}64. {browse "http://www.stata-journal.com/sjpdf.html?articlenum=st0007":http://www.stata-journal.com/sjpdf.html?articlenum=st0007} {title:Also see} Manual: {hi:[R] signrank} On-line: {help signrank}