Stata 14 on Windows
|Original author(s)||Bill Gould|
|Stable release||14.0 / April 7, 2015|
|Operating system||Windows, Mac OS X, Unix, Linux|
Stata is a general-purpose statistical software package created in 1985 by StataCorp. Most of its users work in research, especially in the fields of economics, sociology, political science, biomedicine and epidemiology.
Stata's capabilities include data management, statistical analysis, graphics, simulations, regression, and custom programming.
The name Stata is a syllabic abbreviation of the words statistics and data. The correct English pronunciation of Stata "must remain a mystery"; any of "Stay-ta", "Sta-ta" or "Stah-ta" are considered acceptable.
There are four major builds of each version of Stata:
- Stata/MP for multiprocessor computers (including dual-core and multicore processors)
- Stata/SE for large databases
- Stata/IC, which is the standard version
- Small Stata, which is a smaller, student version for educational purchase only
Stata has always emphasized a command-line interface, which facilitates replicable analyses. Starting with version 8.0, however, Stata has included a graphical user interface which uses menus and dialog boxes to give access to nearly all built-in commands. This generates code which is always displayed, easing the transition to the command line interface and more flexible scripting language. The dataset can be viewed or edited in spreadsheet format. From version 11 on, other commands can be executed while the data browser or editor is opened.
Data structure and storage
Stata can only open a single dataset at any one time. Stata holds the entire dataset in (random-access or virtual) memory, which limits its use with extremely large datasets. This is mitigated to some extent by efficient internal storage, as there are integer storage types which occupy only one or two bytes rather than four, and single-precision (4 bytes) rather than double-precision (8 bytes) is the default for floating-point numbers.
The dataset is always rectangular in format, that is, all variables hold the same number of observations (in more mathematical terms, all vectors have the same length, although some entries may be missing values).
Data format compatibility
Stata's proprietary file formats are platform independent, so users of different operating systems can easily exchange datasets and programs. Stata's data format has changed over time, although not every Stata release includes a new dataset format. Every version of Stata can read all older dataset formats, and can write both the current and most recent previous dataset format, using the saveold command. Thus, the current Stata release can always open datasets that were created with older versions, but older versions cannot read newer format datasets.
Stata can read and write SAS XPORT format datasets natively, using the fdause and fdasave commands.
Stata allows user-written commands, distributed as so-called ado-files, to be straightforwardly downloaded from the internet which are then indistinguishable to the user from the built-in commands. In this respect, Stata combines the extensibility more often associated with open-source packages with features usually associated with commercial packages such as software verification, technical support and professional documentation. Some user-written commands have later been adopted by StataCorp to become part of a subsequent official release after appropriate checking, certification, and documentation.
Stata has an active email list ("Statalist", over 1000 messages per month), to which StataCorp employees regularly contribute. Statalist is maintained by Marcello Pagano of the Harvard School of Public Health, and not by StataCorp itself.
Articles about the use of Stata and new user-written commands are published in the quarterly peer-reviewed Stata Journal. The Stata Journal is a quarterly publication containing articles about statistics, data analysis, teaching methods, and effective use of Stata's language.
User Group meetings are held annually in the United States (the Stata Conference), the UK, Germany, and Italy, and less frequently in several other countries. Only the annual Stata Conference held in the United States is hosted by StataCorp LP. Local Stata distributors host User Group meetings in their own countries, however, Stata developers frequently travel to and present at these meetings. Established under the Societies Act on 10 May 2008, Singapore Stata Users Group is the world's first government-approved users group (Registration No: 2048/2008; Unique Entity No: T08SS0091A). Its slogan is "Shaping Data Meaningfully". As a non-profit organisation, StataUGS does not organise regular meetings but provides programming and statistical advice to users in Singapore through informal means. The active members of StataUGS are mostly engaged in biomedical research.
Example Stata code
To perform logistic regression of y on x:
logistic y x
To display a scatter plot of y against x restricted to values of x below 10:
scatter y x if x < 10
To perform OLS regression of y on x with White's heteroscedasticity-consistent standard errors:
regress y x, vce(robust)
Timeline of releases
Since 2000, StataCorp have released a new major release of Stata (incrementing the integer part of the version number) roughly every two years. Users must pay a fee if they wish to upgrade to the latest major release. Minor releases (incrementing the decimal part of the version number) are sometimes made available between major releases. These are available as free downloadable updates to those who have a licence for the previous major release. Dates of all releases are available on the Stata website. Stata 14 released on April 7, 2015.
Stata's versioning system is designed to give a very high degree of backward compatibility, ensuring that code written for previous releases continues to work. However, users should be careful when they save or open data among different versions.
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