help postfile, help post, help postclose, help postutil
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Title
[P] postfile -- Save results in Stata dataset
Syntax
Declare variable names and filename of dataset where results will be
stored
postfile postname newvarlist using filename [, every(#) replace]
Add new observation to declared dataset
post postname (exp) (exp) ... (exp)
Declare end to posting of observations
postclose postname
List all open postfiles
postutil dir
Close all open postfiles
postutil clear
Description
These commands are utilities to assist Stata programmers in performing
Monte Carlo-type experiments.
postfile declares the variable names and the filename of a (new) Stata
dataset where results will be stored.
post adds a new observation to the declared dataset.
postclose declares an end to the posting of observations. After
postclose, the new dataset contains the posted results and may be loaded
using use; see [D] use.
postutil dir lists all open postfiles. postutil clear closes all open
postfiles.
All five commands manipulate the new dataset without disturbing the data
in memory.
If filename is specified without an extension, .dta is assumed.
Options
every(#) specifies results are to be written to disk every #th call to
post. post temporarily holds results in memory and periodically
opens the dataset being built to append to the stored results.
every() should typically not be specified, because you are unlikely
to choose a value for # that is as efficient as the number post
chooses on its own, which is a function of the number of results
being written and their storage type.
replace indicates that the file specified may already exist, and if it
does, that postfile may erase the file and create a new one.
Remarks
The typical use of the post commands is
tempname memhold
tempfile results
...
postfile `memhold' ... using `results'
...
while ... {
...
post `memhold' ...
...
}
postclose `memhold'
...
Two names are specified with postfile: postname is a name assigned to
internal memory buffers, and filename is the name of the file to be
created. Subsequent posts and the postclose are followed by postname so
that Stata will know to what file they refer.
In our sample, we obtain both names from Stata's temporary name facility
(see [P] macro), although, in some programming situations, you may wish
to substitute a hard-coded filename. We recommend that postname always
be obtained from tempname. This ensures that your program can be nested
within any other program and ensures that the memory used by post is
freed if anything goes wrong. Using a temporary filename, too, ensures
that the file will be erased if the user presses Break. Sometimes,
however, you may wish to leave the file of incomplete results behind.
That is allowed, but remember that the file is not fully up to date if
postclose has not been executed. post buffers results in memory and only
periodically updates the file.
Because postfile accepts a newvarlist, storage types may be interspersed,
so you could have
postfile `memhold' a b str20 c double(d e f) using "`results'"
Also see
Manual: [P] postfile
Help: [R] bootstrap, [R] simulate
