whatsnew6to7.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}
{* 08apr2005}{...}
{cmd:help whatsnew6to7}
{hline}

{title:What's new in release 7 (compared to release 6)}

{pstd}
This help file lists the changes corresponding to the creation of Stata
release 7:

    {c TLC}{hline 67}{c TRC}
    {c |} help file       contents                   dates                  {c |}
    {c LT}{hline 67}{c RT}
    {c |} {help whatsnew}        Stata 9.0                  22apr2005 to present   {c |}
    {c |} {help whatsnew8to9}    Stata 9.0 new release      22apr2005              {c |}
    {c |} {help whatsnew8_2}     Stata 8.2                  28oct2003 to 24feb2005 {c |}
    {c |} {help whatsnew8_1}     Stata 8.1                  01jul2003 to 30sep2003 {c |}
    {c |} {help whatsnew8_0}     Stata 8.0                  14jan2003 to 25jun2003 {c |}
    {c |} {help whatsnew7to8}    Stata 8.0 new release      02jan2003              {c |}
    {c |} {help whatsnew7}       Stata 7.0                  08jan2001 to 05dec2002 {c |}
    {c |} {bf:this file}       Stata 7.0 new release      15dec2000              {c |}
    {c |} {help whatsnew6}       Stata 6.0                  13jan1999 to 20nov2000 {c |}
    {c BLC}{hline 67}{c BRC}

{pstd}
Most recent changes are listed first.


{hline 3} {hi:more recent updates} {hline}

{pstd}
See {help whatsnew7}.


{hline 3} {hi:Stata 7 release 15dec2000} {hline}

{p 4 4}The features added to Stata 7 are listed under the following headings.

{p 8 12}Changes you cannot help but notice{p_end}
{p 16 20}Long (32-character) names{p_end}
{p 16 20}New varlist abbreviation rules{p_end}
{p 16 20}Windowed Stata now across all platforms{p_end}
{p 16 20}Improved output, more clickability{p_end}
{p 16 20}Improvements to by{p_end}
{p 16 20}Sort stability{p_end}
{p 16 20}European decimal format{p_end}
{p 16 20}Faster{p_end}

{p 8 12}Statistics{p_end}
{p 16 20}Estimation commands (exclusive of st and xt){p_end}
{p 16 20}Cross-sectional time-series analysis (xt){p_end}
{p 16 20}Survival analysis (st){p_end}
{p 16 20}Commands for epidemiologists{p_end}
{p 16 20}Marginal effects{p_end}
{p 16 20}Cluster analysis{p_end}
{p 16 20}Pharmacokinetics{p_end}
{p 16 20}Other statistical commands{p_end}
{p 16 20}Distribution functions{p_end}

{p 8 12}Nonstatistical improvements{p_end}
{p 16 20}Graphics{p_end}
{p 16 20}New commands{p_end}
{p 16 20}New string functions{p_end}
{p 16 20}Other new functions{p_end}


{hline}

{title:Changes you cannot help but notice}

    {title:Long (32-character) names}

{p 4 4}
Stata now allows names to be up to 32 characters long.  That includes variable
names, label names, macro names, and any other name you can think of.  This
includes program names, and we have renamed a few existing Stata programs:

{center:Prior name    New name  }
{center:{hline 24}}
{center:{cmd:llogist}       {help llogistic} }
{center:{cmd:xthaus}        {help xthausman} }
{center:{cmd:spikeplt}      {help spikeplot} }
{center:{cmd:stcurv}        {help stcurve}   }
{center:{cmd:svyintrg}      {help svyintreg} }
{center:{cmd:svyprobt}      {help svyprobit} }
{center:{cmd:svymlog}       {help svymlogit} }
{center:{cmd:svyolog}       {help svyologit} }
{center:{cmd:svyoprob}      {help svyoprobit}}

{p 4 4}
The old names continue to work.

{p 4 4}
In any case, now you do not have to name your variable {hi:f_inc1999}, you can
name it {hi:farm_inc_1999} or {hi:farm_income_1999} or even
{hi:farm_income_in_fiscal_year_1999}.  Where possible, we have adjusted Stata
output to allow 12 spaces for displaying names.  When names are longer than
that, you will discover that Stata abbreviates and shows, for instance,
{hi:farm_in~1999}.  {hi:~} is the new Stata abbreviation character, which
Stata not only uses in output but which you can use in input (which is to say,
in varlists; see help {help varlist}).  If you type {hi:farm_in~1999},
{hi:f~1999}, or {hi:f~in~1999}, Stata will understand that you mean
{hi:farm_income_in_fiscal_year_1999}.  Thus, if in output Stata presents
{hi:dose~d1~42}, that name is unique and you can type it and Stata will
understand it.

{p 4 4}
{help describe} now has two new options, {cmd:fullname} and {cmd:numbers}.
{cmd:fullname} shows the full, 32-character names, instead of shorter
{hi:~}-abbreviations, and {cmd:numbers} shows the variable number.


    {title:New varlist abbreviation rules}

{p 4 4}
Varlists now understand {cmd:*} when used as other than a suffix.  You can
still type {hi:pop*}, but you can also type {hi:pop*99} or {hi:pop*30_40*1999}
or even {hi:*1999}.  {cmd:*} means "zero or more characters go here".  Also
understood is the new {cmd:~} abbreviation character mentioned above.  {cmd:*}
and {cmd:~} really mean the same thing and work the same way, except {cmd:~}
adds the claim "and only one variable matches this pattern", whereas {cmd:*}
means "give me all the variables that match this pattern".

{p 4 4}
The other new abbreviation character is {cmd:?}, which means "one character
goes here", so {hi:result?10} might match {hi:resultb10} and {hi:resultc10},
but would not match {hi:resultb110}.


    {title:Windowed Stata now across all platforms}

{p 4 4}
Stata for Unix users now have the same windowed interface that Stata for
Windows and Stata for Macintosh users have:  type {cmd:xstata} rather than
{cmd:stata} to start Stata.  Typing {cmd:stata} brings up the old line-by-line
console version of Stata.  Typing {cmd:xstata} brings up the new windowed
version.  The old console version is still useful in batch situations, but
Stata(console), as it is now called, can no longer render graphs.


    {title:Improved output, more clickability}

{p 4 4}
Stata's output looks better thanks to the new output language called SMCL,
which stands for Stata Markup and Control Language.  Moreover, all Stata
output, whether it be help files in the help window (now called the Viewer),
help files in the Results window, or statistical output, is SMCL, meaning all
features are available in all contexts.  One implication is that if something
is clickable, it is clickable regardless of the window in which it is
displayed, so you can start by typing {cmd:help} {cmd:anova} and click on
links just as you could had you pulled down {hi:Help} and gone about
displaying the help in the help window (Viewer).

{p 4 4}
Clickability is not limited to help files.  You can write programs that
display in their output clickable links.  The corresponding action can even be
the execution of another Stata command or program!

{p 4 4}
The help window is now called the Viewer because it serves more purposes than
solely displaying help files.  The Viewer, for instance, is where you look at
logs you have previously created or are creating.  That's because, by default,
Stata logs are now SMCL files and the default file extension for log files is
{hi:.smcl} to remind you of that.  When you type `{cmd:log using myfile}',
{hi:myfile.smcl} is created.  The file is ASCII, so you can look at it (and
even edit it) in your editor or word processor, but it is not a pretty sight.

{p 4 4}
Formatted, however, it is pretty.  The Viewer can print the SMCL logs Stata
now creates, and the new {cmd:translate} command can translate the SMCL file
to PostScript format, or even standard ASCII text format, so you can get back
to just where you were in Stata 6; see help {help translate}.  Moreover, you
can directly create old-style ASCII text logs if that is your preference; just
type `{cmd:log using myfile.log}' or `{cmd:log using myfile, text}'; see help
{help log}.

{p 4 4}
The Viewer can be accessed by pulling down {hi:File}, or you can use the new
{cmd:view} command, which provides some additional features; see help
{help view}.

{p 4 4}
Programmers will want to see help {help smcl} for a complete description of
SMCL.  You can use SMCL in your ado-files.

{p 4 4}
There is one other log change:  you can now create command logs (ASCII text
logs containing only what you type, which used to be called {cmd:noproc} logs)
using the new {cmd:cmdlog} command.  Even better, you can create command logs
and full session logs simultaneously; see help {help log}.

{p 4 4}
Stata(console) for Unix users:  All of the above applies to you, too, except
that you cannot click.  Stata(console) does not have a {cmd:view} command, but
{cmd:type} can display {hi:.smcl} files, and {cmd:translate} can translate
them.  See help {help conren} for instructions on how to make SMCL output look
as good as possible on your line-by-line console.


    {title:Improvements to by}

{p 4 4}
{cmd:by} {it:varlist}{cmd::} now has a {cmd:sort} option.  You can type, for
instance, `{cmd:by foreign, sort: summarize mpg}' or, equivalently,
`{cmd:bysort foreign: summarize mpg}', rather than first sorting
the data and then typing the {cmd:by} command; see help {help by}.

{p 4 4}
{cmd:by} has a new parenthesis notation:
`{cmd:by} {it:id} {cmd:(}{it:time}{cmd:):} {it:...}' means to perform {it:...}
by {it:id}, but first verify that the data are sorted by {it:id} and
{it:time}.  `{cmd:by} {it:id} {cmd:(}{it:time}{cmd:), sort:} {it:...}' says to
sort the data by {it:id} and {it:time} and then perform {it:...} by {it:id}.

{p 4 4}
There is also a new {cmd:rc0} option, which says to keep on going even if one
of the by-groups results in an error.

{p 4 4}
More importantly, {cmd:by} {it:varlist}{cmd::} is now allowed with virtually
every Stata command, including commands implemented as ado-files, including
{cmd:egen}.  We have been claiming for some time that whether a command is
built-in or implemented as an ado-file is irrelevant, it has the same
features.  Now the claim is true.  Programmers:  see help {help byprog} for
instructions on how to make your programs and ado-files allow the {cmd:by}
prefix; it is easy.

{p 4 4}
The commands {cmd:generate}, {cmd:replace}, {cmd:drop}, {cmd:keep}, and
{cmd:assert} no longer present the detailed, group-by-group report when
prefixed with {cmd:by}, meaning you no longer need to prefix them with
{cmd:quietly}:

{p 8 12}{cmd:. by id:  replace bp = bp[_n-1] if bp==.}{p_end}
{p 8 12}{txt:(120 changes made)}


    {title:Sort stability}

{p 4 4}
Commands that report results of calculations (commands not intended to change
the data) no longer change the sort order of the data.  If you type
`{cmd:sort} {it:id} {it:time}', you can be assured that your dataset will stay
sorted by {it:id} and {it:time}. This is true even if the command is
implemented as an ado-file.

{p 4 4}
Programmers:  see {hi:[P] sortpreserve} for instructions on making your old
programs and ado-files sort stable.  It is easy, and the performance penalty
is barely measurable.


    {title:European decimal format}

{p 4 4}
Stata now understands output formats such as {cmd:%9,2f} as well as
{cmd:%9.2f}.  In {cmd:%9,2f}, the number 500.5 is displayed as 500,50.  In
{cmd:%9,2fc} format, the number 1,000.5 is displayed as 1.000,50.

{p 4 4}
Even better, you can now {cmd:set dp comma} to modify all of Stata's output to
use the European format, including all statistical output.  See help
{help format}.


    {title:Faster}

{p 4 4}
Stata 7 has more features, but continuing our long tradition, it is also
faster; ado-files execute between 8.8 and 11.8 percent faster.  Some programs,
we have observed, execute 13 percent faster.


{hline}

{title:Statistics}

    {title:Estimation commands (exclusive of st and xt)}

{p 4 4}
First, all maximum-likelihood estimation commands of Stata now allow linear
constraints; each has a new {cmd:constraint()} option.  See the particular
estimator.

{p 4 4}
{cmd:boxcox} has been rewritten.  It now produces maximum likelihood estimates
of the coefficients and the Box--Cox transform parameter(s).  Box--Cox models
may be estimated in various forms, with the transform on the left, on the
right, or on both sides.  See help {help boxcox}.

{p 4 4}
{cmd:glm} has also been rewritten.  It continues to estimate the generalized
linear model, but now offers an expanded choice of link functions and also
allows user-specified link and variance functions.  {cmd:glm} will now report
maximum-likelihood based estimates of standard errors, IRLS based estimates,
and many others.  See help {help glm}

{p 4 4}
{cmd:nlogit} estimates nested logit models.  In a nested logit model, multiple
outcomes are grouped into a nested tree structure, and nested logit has the
advantage over multinomial and conditional logistic models of allowing you to
parameterize away the assumption of independence of the irrelevant
alternatives (IIA).  See help {help nlogit}.

{p 4 4}
{cmd:treatreg} estimates the treatment effects model using either a two-step
estimator or a full maximum-likelihood estimator.  The treatment effects model
considers the effect of an endogenously chosen binary treatment on another
endogenous continuous variable, conditional on two sets of independent
variables.  See help {help treatreg}.

{p 4 4}
{cmd:truncreg} estimates truncated regression models.  Truncated regression
refers to regressions estimated on samples drawn based on the dependent
variable, and therefore for which (sometimes) neither the dependent nor
independent variables are observed (as opposed to {cmd:tobit}, which estimates
regression models when the independent variables are observed in all cases).
See help {help truncreg}.


    {title:Cross-sectional time-series analysis (xt)}

{p 4 4}
{cmd:xtabond} produces the Arellano--Bond one-step, one-step
    robust, and two-step estimators for dynamic panel-data models, models in
    which there are lagged dependent variables.  {cmd:xtabond} can be used
    with exogenously unbalanced panels and, uniquely, handles embedded gaps in
    the time series as well as opening and closing gaps.  {cmd:xtabond} allows
    for predetermined covariates.  {cmd:xtabond} allows you to use either the
    full instrument matrix or a pared down version.  {cmd:xtabond} reports
    both the Sargan and autocorrelation tests derived by Arellano and Bond.
    See help {help xtabond}.