{smcl} {hline} {cmd:help parmby_only_opts}{right:(Roger Newson)} {hline} {title:Options for {helpb parmby} only} {title:Syntax} {synoptset 24} {synopthdr} {synoptline} {synopt:{cmd:by(}{varlist}{cmd:)}}Specify variables defining by-groups{p_end} {synopt:{opt com:mand}}Add a variable containing the command called{p_end} {synoptline} {title:Description} {pstd} These options may not be specified for {helpb parmest}. They allow the user to call an {help estcom:estimation command} once for each of a set of by-groups, and to create an the output dataset (or resultsset) with one observation per parameter per by-group. {title:Options} {p 4 8 2} {cmd:by(}{it:varlist}{cmd:)} specifies a list of existing variables which would normally appear in the {help by:{cmd:by} {it:varlist}{cmd::}} section of the Stata estimation command called by {helpb parmby}. {helpb parmby} creates an output dataset with one observation for each parameter in each by-group in which the command executed successfully. The output dataset contains values of the by-variables in each by-group (if {cmd:by()} is specified), in addition to the variables created by {helpb parmest}. However, the {cmd:by()} option is optional, and {helpb parmby} will still work without it, creating an output dataset with one observation per parameter of a single set of estimation results. {p 4 8 2} {opt command} is a {help parmest_varadd_opts:variable-adding option}. If specified, it creates a string variable named {hi:command} in the output dataset, containing the text of the {help estcom:estimation command} called by {helpb parmby}. The text of the command is truncated, if necessary, to the maximum length of a string variable under the edition of Stata currently in use, which is 244 characters in {help version:Stata Version 9}. (See help for {help limits}.) The variable {hi:command} has the same value in all observations in the output dataset, and is useful as an identifier if the user creates multiple {helpb parmby} output datasets, using different commands, and concatenates them using {helpb append}, or using {helpb dsconcat} if installed. {title:Notes} {pstd} Note that the variable {hi:command} can be renamed by the {cmd:rename()} option, but the variables specified in {cmd:by(}{varlist}{cmd:)} cannot. See help for {help parmest_varmod_opts:{it:parmest_varmod_opts}} for details on the {cmd:rename()} option, and help for {help parmest_resultssets:{it:parmest_resultssets}} for details of other variables in the output datasets (or resultssets} produced by {helpb parmest} and {helpb parmby}. {title:Author} {pstd} Roger Newson, Imperial College London, UK. Email: {browse "mailto:r.newson@imperial.ac.uk":r.newson@imperial.ac.uk} {title:Also see} {p 4 13 2} {bind: }Manual: {hi:[D] append}, {hi: [D] by}, {hi: [U] 11.4 varlists}, {hi: [U] 20 Estimation and postestimation commands} {p_end} {p 4 13 2} On-line: help for {helpb append}, {helpb by}, {varlist}, {help estcom:estimation commands} {break} help for {helpb parmest}, {helpb parmby}, {help parmest_outdest_opts:{it:parmest_outdest_opts}}, {help parmest_ci_opts:{it:parmest_ci_opts}}, {help parmest_varadd_opts:{it:parmest_varadd_opts}}, {help parmest_varmod_opts:{it:parmest_varmod_opts}}, {help parmest_resultssets:{it:parmest_resultssets}} {break} help for {helpb dsconcat} if installed {p_end}