prefix.hlp

是一个经济学管理应用软件 很难找的 但是经济学学生又必须用到

{smcl}
{* 19feb2005}{...}
{cmd:help prefix}
{hline}

{title:Title}

{p 4 13 2}{hi:[U] 11.1.10 Prefix commands}


{title:Syntax}

	{it:prefix ...}{cmd::} {it:command} {it:...}

{p2colset 5 18 20 2}{...}
{p2col:{it:prefix}}description{p_end}
{p2line}
{p2col:{helpb by}}run command on subsets of data{p_end}
{p2col:{helpb statsby}}same as {cmd:by}, but collect statistics from each
	run{p_end}
{p2col:{helpb rolling}}run command on moving subsets, and collect
	statistics{p_end}

{p2col:{helpb bootstrap}}run command on bootstrap samples{p_end}
{p2col:{helpb jackknife}}run command on jackknife subsets of data{p_end}
{p2col:{helpb permute}}run command on random permutations{p_end}
{p2col:{helpb simulate}}run command on manufactured data{p_end}

{p2col:{helpb svy}}run command and adjust results for survey sampling{p_end}
{p2col:{helpb stepwise}}run command with stepwise variable
	inclusion/exclusion{p_end}
{p2col:{helpb xi}}run command after expanding factor variables & 
	interactions{p_end}

{p2col:{helpb capture}}run command and capture its return code{p_end}
{p2col:{helpb noisily}}run command and show the output{p_end}
{p2col:{helpb quietly}}run command and suppress the output{p_end}
{p2col:{helpb version}}run command under specified version{p_end}
{p2line}
{p2colreset}{...}

{pstd}
The last group{hline 2}{cmd:capture}, {cmd:noisily}, {cmd:quietly}, and
{cmd:version}{hline 2}have to do with programming Stata and, for historical
reasons, {cmd:capture}, {cmd:noisily}, and {cmd:quietly} allow you to omit
the colon.


{title:Description}

{pstd}
Prefix commands operate on other Stata commands.  They modify the input,
modify the output, or repeat execution of the {it:command}.  For example,
{helpb xi} modifies the {varlist} of {it:command}.  {helpb svy} modifies the
results of {it:command} to account for complex survey data.  {helpb by}
executes {it:command} on subgroups of the data.

{pstd}
See {help language} for an overview of the Stata language.


{title:Remarks}

{pstd}
Prefix commands are not allowed in all contexts.  For instance, {helpb svy} and
{helpb stepwise} may only be used on supported estimation commands.  {helpb bootstrap},
{helpb jackknife}, ... make no sense when combined with a command like
{helpb generate}.

{pstd}
Many of the prefix commands can be combined.  For instance,

{phang2}
{cmd:xi: svy: logit diabetes female i.agegroup}

{pstd}
However, some combinations of prefix commands are not allowed.  For example,

{phang2}
{cmd:bootstrap: statsby: logit diabetes female age}

{pstd}
is not allowed because statsby saves results to a dataset and not in {cmd:r()}
or {cmd:e()}.


{title:Examples}

{phang}{cmd:. xi: regress y i.agegrp*wght}

{phang}{cmd:. bs, reps(1000): logit diabetes female age}

{phang}{cmd:. by group: assert _N > 5}

{phang}{cmd:. statsby r(min) r(max), by(group) clear: summarize income}


{title:Also see}

{psee}
Manual:  {bf:[U] 11.1.10 Prefix commands}

{psee}
Online:  {help language};
{help estcom};
{helpb bootstrap},
{helpb by},
{helpb capture},
{helpb jackknife},
{helpb permute},
{helpb quietly},
{helpb rolling},
{helpb simulate},
{helpb statsby},
{helpb svy},
{helpb stepwise},
{helpb version},
{helpb xi}
{p_end}