{smcl}
{* Apr2011}{...}
{hline}
help for {hi:obsdiff}
{hline}

{title: Identify differences in values across observations for a variable.}

{p 4 8 2} 
{cmd:obsdiff}
{it:varlist} 
[{cmd:if} {it:exp}] 
[{cmd:using} {it:newfile}]
[
{cmd:,} 
{cmdab:r:ows(}{it:numlist}{cmd:)}
{cmdab:rep:lace} 
{cmdab:all} ]
{break} 
 
{title:Description}

{p 2 2 4}
{cmd:obsdiff} lists the differences among observations/records in a varlist. 
This program is particularly useful for data where observations are near duplicates and you 
need to identify the variables that differ. In this way, {cmd:obsdiff} operates similar
to {help duplicates list} except that it lists {bf:differences} (not duplicates) for the 
{it:varlist} in the range of observations/records specified in the option {opt rows}.  The 
output can be saved to a text file with the {opt using} option.

{title: Options} 

{p 4 8 2}
{cmdab:r:ows(}{it:numlist}{cmd:)} required unless {opt all} is specified.  This option
identifies the range of rows or observations that should be examined for differences for
each variable in the {it: varlist}.  The format for the {it: numlist} is explained 
in {help numlist}.

{p 4 8 2}
{cmdab:rep:lace} overwrites {it: newfile}.txt, if it exists.

{p 4 8 2}
{cmdab:all} is used in place of the {opt range} option to indicate that all observations 
should be examined for differences among the variables in the {it: varlist}.  Same as specifying
{bf: rows(1/`=_N')}.

{p 4 8 2}
{cmd:if} is allowed.

{p 4 8 2}
{bf:{it: `r(diff_vars)'}} contains a list of variables in {it: varlist} with differences in 
the specified {opt rows}.

{title: Examples}

{p 4 8 2}{cmd:. sysuse auto, clear}{p_end}
{p 4 8 2}{cmd:. obsdiff make for rep78 , r(8/12)}{p_end}
{p 4 8 2}{cmd:. di "`r(diff_vars)'" } {p_end}

{p 4 8 2}{cmd:. obsdiff for rep78, all}{p_end}
{p 4 8 2}{cmd:. obsdiff rep78 if for==0, r(1/10)} {p_end}
{p 4 8 2}{cmd:. obsdiff rep78 if for==1 using "obsdiff_log", all replace}{p_end}


{title:Author}

{p 4 4 2}Eric A. Booth, Texas A&M University {break} 
         ebooth@ppri.tamu.edu {break} 
		 {browse "http://www.eric-a-booth.com"}
		 
{title:Also see}

{p 4 8 2}On-line:  help for {help list:list}; {help duplicates list:duplicates list}; {help unique:unique}(if installed)