lv.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}
{* 03dec2004}{...}
{cmd:help lv}{right:dialog:  {bf:{dialog lv}}}
{hline}

{title:Title}

{p2colset 5 15 17 2}{...}
{p2col :{hi:[R] lv} {hline 2}}Letter-value displays{p_end}
{p2colreset}{...}


{title:Syntax}

{p 8 12 2}
{cmd:lv} [{varlist}] {ifin} [{cmd:,} {opt g:enerate} {opt t:ail(#)}]

{phang}
{opt by} may be used with {cmd:lv}; see {helpb by}.


{title:Description}

{pstd}
{cmd:lv} shows a letter-value display for each variable in {varlist}.  If no
variables are specified, letter-value displays are shown for each numeric
variable in the data.


{title:Options}

{dlgtab:Main}

{phang}
{opt generate} adds four new variables to the data:  {opt _mid}, containing
the midsummaries; {opt _spread}, containing the spreads; {opt _psigma},
containing the pseudosigmas; and {opt _z2}, containing the squared values from
a standard normal distribution corresponding to the particular letter value.
If the variables {opt _mid}, {opt _spread}, {opt _psigma}, and {opt _z2}
already exist, their contents are replaced.  At most, only the first 11
observations of each variable are used; the remaining observations contain
missing.  If {varlist} specifies more than one variable, the newly created
variables contain results for the last variable specified.  The {opt generate}
option may no be used with the {cmd:by} prefix.

{phang}
{opt tail(#)} indicates the inverse of the tail density through which letter
values are to be displayed.  2 corresponds to the median (meaning half in each
tail), 4 to the fourths (roughly the 25th and 75th percentiles), 8 to the
eighths, and so on. {it:#} may be specified as 4, 8, 16, 32, 64, 128, 256,
512, or 1,024 and defaults to a value of {it:#} that has corresponding depth
just greater than 1.  The default is taken as 1,024 if the calculation results
in a number larger than 1,024.  Given the intelligent default, this option is
rarely specified.


{title:Examples}

{phang}{cmd:. lv mpg}{p_end}
{phang}{cmd:. lv mpg, generate}{p_end}
{phang}{cmd:. scatter _mid _z2}{space 8}(Diagnostic for skewness){p_end}
{phang}{cmd:. scatter _psigma _z2}{space 5}(Diagnostic for elongation)


{title:Also see}

{psee}
Manual:  {bf:[R] lv}

{psee}
Online:  {help diagnostic plots}, {helpb stem}, {helpb summarize}
{p_end}