Learning more about Stata

1. Where to go from here You now know plenty enough to use Stata. There is still much, much more to learn because Stata is a rich environment for doing statistical analysis and data management. What should you do to learn more? Get an interesting dataset and play with Stata. Use the menus and

Updating and extending Stata—Internet functionality

1. Internet functionality in Stata Stata works well with the Internet. Stata can use datasets and view remote help files as though they were on your computer. Stata also can keep itself up to date (with your permission, of course). Finally, you can install community-contributed commands, which are commands that extend Stata’s functionality. These

Troubleshooting Stata

1. If Stata does not start You tried to start Stata and it refused; Stata or your operating system presented a message explaining that something is wrong. Here are the possibilities: Cannot find license file This message means just what it says; nothing is too seriously wrong. Stata simply could not find the license

Advanced Stata usage

1. The Windows Properties Sheet When you double-click on a shortcut to start an application in Windows, you are actually executing instructions defined in the shortcut’s Properties Sheet. To open the Properties Sheet for any shortcut, right-click on the shortcut, and select Properties. Open the Properties Sheet for Stata’s shortcut. Click on the Shortcut

More on Stata for Windows

1. Using Stata datasets and graphs created on other platforms Stata will open any Stata .dta dataset or .gph graph file regardless of the platform on which it was created, even if it was a Mac or Unix system. Also Stata for Mac and Stata for Unix users can use any files that you

Typographical Note and Example Stata Session

1. Typographical Note This book employs several typographical conventions as a visual cue to how words are used: ■ Commands typed by the user appear in bold. When the whole command line is given, it starts with a period, as seen in a Stata Results window or log (output) file: . correlate extent area

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Stata Documentation and Resources

1. Stata’s Documentation and Help Files The complete Stata 12 Documentation Set includes 19 volumes: a slim Getting Started manual (for example, Getting Started with Stata for Windows), the more extensive User’s Guide, the encyclopedic four-volume Base Reference Manual, and separate reference manuals on data management, graphics, longitudinal and panel data, matrix programming (Mata),

Creating a New Stata Dataset by Typing in Data

Data that were previously saved in Stata format can be retrieved into memory either by typing a command of the form use filename, or by menu selections. This section describes basic tricks for creating Stata-format datasets in the first place. We could start simply by typing data into the Data Editor by hand. A

Creating a New Stata Dataset by Copy and Paste

When the original data source is electronic, such as a web page, text file, spreadsheet or word processor document, we can bring these data into Stata by copy and paste. For example, the National Climate Data Center (NCDC) produces estimates of global temperature anomalies (deviations from the 1901-2000 mean, in degrees Celsius) for every

Specifying Subsets of the Data: in and if Qualifiers

Many Stata commands can be restricted to a subset of the data by adding an in or if qualifier. Qualifiers are also available for many menu selections: look for an if/in or by/if/in tab along the top of the dialog. in specifies the observation numbers to which the command applies. For example, list in

Generating and Replacing Variables in Stata

The generate and replace commands allow us to create new variables or change the values of existing variables. For example, in Canada, as in most industrial societies, women tend to live longer than men. To analyze regional variations in this gender gap, we might retrieve dataset Canadal.dta and generate a new variable equal to

Missing Value Codes in Stata

Examples seen so far involve only a single missing-value code, Stata’s default: a large number which Stata displays as a period. In some datasets, however, values might be missing for several different reasons. We could denote different kinds of missing values by using extended missing- value codes. These are even larger numbers, which Stata

Using Functions in Stata

This section lists many of the functions available for use with generate or replace. For example, we could create a new variable named loginc, equal to the natural logarithm of income, by using the natural log function ln in a generate command: . generate loginc = ln(income) ln is one of Stata’s mathematical functions.

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Converting Between Numeric and String Formats in Stata

Dataset Canada2.dta contains one string variable, place. It also has a labeled categorical variable, type. Both seem to have nonnumeric values. Beneath the labels, however, type remains a numeric variable, indicated by a blue font in the Data Editor or Browser. Clicking on that cell will show the underlying numbers, or we can list

Creating New Categorical and Ordinal Variables in Stata

A previous section illustrated how to construct a categorical variable called type to distinguish among territories, provinces and nation in our Canadian dataset. You can create categorical or ordinal variables in many other ways. This section gives a few examples. Suppose we want to re-express type as a set of dichotomies or dummy variables,

Using Explicit Subscripts with Variables in Stata

When Stata has data in memory, it also defines certain system variables that describe those data. For example, _N represents the total number of observations. _n represents the observation number: _n = 1 for the first observation, _n = 2 for the second, and so on to the last observation ( _n = _N

Importing Data from Other Programs to Stata

Previous sections illustrated how to enter and edit data using the Data Editor. If our original data reside in an appropriately formatted spreadsheet, we just can copy and paste blocks of data from the spreadsheet into the empty Data Editor. Alternatively, Stata can import data from Excel spreadsheets directly through menu selections File >

Combining Two or More Stata Files

We can combine Stata datasets in two general ways: append a second dataset that contains additional observations, or merge with other datasets that contain new variables or values. For example, file lakewinl.dta contains the ice-out dates for New Hampshire’s largest lake, recorded by local observers over 121 years from 1887 through 2007. In 2007,

Collapsing Data in Stata

Long after a dataset has been created, we might discover that for some purposes it has the wrong organization. Fortunately, several commands facilitate drastic restructuring of datasets. The simplest of these, collapse, aggregates data into means, medians or other statistics for groups defined by one or more variables. For illustration, we return to the

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Reshaping Data in Stata

A different sort of restructuring is possible through the reshape command. This command switches datasets between two basic configurations termed wide and long. Earlier in this chapter we built a dataset with the Multivariae ENSO Index (MEIO.dta). The data are in wide format: years define the rows, but each month is a separate column.