{smcl} {* 11Mar2009}{...} {hline} help for {hi:checkvar} {hline} {title:Produce a table showing the relationship between a created variable and its component variables} {p 8 17 2} {cmd:checkvar} {it:created-variable} {it:varlist} {ifin} {title:Description} {p 4 4 2}{cmd:checkvar} displays a table showing each value of a created variable, followed by each unique combination of values of the component variables and the frequency of each combination. The {it:created-variable} should be listed first after the command, then each component variable that was used to create it. {p 4 4 2}{cmd:checkvar} can also be used to examine patterns of respondents in a set of skip and filter questions in a survey. In this case the first substantive question following the skips and filters should be viewed as the created variable and the skips and filtes as the component variables. {title:Remarks} {p 4 4 2} This command is more useful if the created and component variables have few discrete values than if they have a large number of values. {title:Example - created variable} {p 4 8 2}{cmd:. sysuse auto} {p 4 8 2}{cmd:. gen byte goodcar=(rep78>=3 & headroom>3 & trunk>15)} {p 4 8 2}{cmd:. checkvar goodcar rep78 headroom trunk} {p 4 8 2}{cmd:. replace goodcar=. if rep78==.} {p 4 8 2}{cmd:. checkvar goodcar rep78 headroom trunk} {title:Example - skip pattern} {p 4 8 2}{cmd:. checkvar q45 q40 q42 q43} {title:Saved Results} {p 4 4 2} If all variables in {it:varlist} are numeric, the checkvar command saves in r() (see help for {help return}): {p 8 8 2}r(combos) - the number of combinations {p 8 8 2}r(checkvar) - the matrix of all combinations and their frequencies {title:Reference} {p 4 4 2} Dan Blanchette and Nick Cox suggested very useful improvements to this command. {title:Author} {p 4 4 2} Phil Bardsley, {browse "http://www.cpc.unc.edu":Carolina Population Center}, University of North Carolina - Chapel Hill, USA. Contact {browse "mailto:phil_bardsley@unc.edu":phil_bardsley@unc.edu} if you observe any problems. {title:Also see} {p 4 13 2} Manual: {hi:[R] tabulate,} {hi:[R] table}, {hi:[R] contract} {p 4 13 2} Online: help for {help tabulate}, {help table}, {help contract}; {help groups} (if installed)