FAQ: Data management

>> Home >> Resources & support >> FAQs >> Data management

Data management

FAQ:		Data management	Search the FAQs:
Last updated:		26 July 2011
Stata release:		12

Questions are listed below in the following categories:

Reading and inputting data
Combining datasets
Memory usage
Data manipulation
4.1 Variable creation
4.2 Short-cuts
4.3 Puzzling results
4.4 Dataset manipulation
4.5 Replacing values or observations
Data reporting
Other
FAQs concerning Stata 11
FAQs concerning releases before Stata 11

1. Reading and inputting data

How do I connect to a database by using a Stata plugin?

How do I export tables from Stata?

Why do I get rows of missing data when I use infile?

How can I convert other packages' files to Stata format data files?

How do I set up an ODBC Data Source Name for Stata on Mac or Linux/Unix?

Stata is reading in my variables as string instead of numeric. What should I do?

How do I convert date variables into Stata elapsed dates when the numbers run together, like “4151999”?

How do I get information from Excel into Stata?

How can I save a Stata dataset so that it can be read in a previous version of Stata?

Why do I get the error “wrong number of values” when I use insheet to read data from Excel?

How do I use infile to read in fixed-format data?

Can infile read in a hierarchical dataset?

2. Combining datasets

How do you process very large datasets in Stata?

3. Memory usage

How big will my dataset be?

4. Data manipulation

4.1 Variable creation

How can I sample clusters, not individuals?

How can I identify first and last occurrences systematically in panel data?

How do I deal with a report of repeated time values within panel?

How can I create variables containing percent summaries?

How can I generate a variable containing the last of several dates?

How do I split a string variable into parts?

What is true and false in Stata?

How do I calculate measures such as percent improved minus percent deteriorated?

How do I create variables summarizing for each individual properties of the other members of a group?

How do I create individual identifiers numbered from 1 upwards?

How do I create a variable recording whether any members of a group (or all members of a group) possess some characteristic?

How do I create dummy variables?

4.2 Short-cuts

How do I perform element-by-element operations on matrices?

How can I list, drop, and keep a consecutive set of variables without typing the names individually?

Can I apply the label values command to more than one variable at the same time? I want to attach the same value labels to several variables.

4.3 Puzzling results

How many significant digits are there in a float?

Why does the mod(x,y) function sometimes give puzzling results? Why is mod(0.3, 0.1) not equal to 0?

Why can’t I compare two values that I know are equal?

Why is x>1000 true when x contains missing values?

Why does my do-file or ado-file produce different results every time I run it?

4.4 Dataset manipulation

How do I calculate the maximum or minimum seen so far in a sequence?

What are regular expressions and how can I use them in Stata?

How do I remove leading or trailing zeros from string variables?

How do I go through the groups of a variable in order of their first occurrence in the dataset?

How can I drop spells of missing values at the beginning and end of panel data?

Is there a way to tell Stata to try all values of a particular variable in a foreach statement without specifying them?

I want to calculate a variable containing weighted group summary statistics, but I do not want to collapse the data and egen does not support weights. How can I do this?

How do I deal with multiple responses?

How can I collapse my dataset and keep the same variable labels?

How do I identify runs of consecutive observations in panel data?

How do I select a subset of observations using a complicated criterion?

How can I save one or more parts of a large dataset?

How do you efficiently define group characteristics in your data in order to create subsets?

How do I perform multiple operations on data records if a condition is met?

I am having problems with the reshape command. Can you give further guidance?

How do I produce a dataset based on all possible pairs of identifiers within each group?

Why doesn't the destring command in Stata include an encode option?

How can I create a dataset (matrix) of means (other stats) of variables from the current dataset?

How do I implement SAS-like ARRAYs in Stata?

4.5 Replacing values or observations

How can I replace missing values with previous or following nonmissing values or within sequences?

How can I replace an observation of a variable with a different observation for another variable?

5. Data reporting

How do I calculate the number of distinct values seen so far?

How do I count the number of distinct strings across a set of variables?

How do I compute the number of distinct observations?

How do I tabulate cumulative frequencies?

How do I list observations in a group that differ on a variable?

Is there a way to put leading zeros in output?

How can I produce a tabulation of a string variable that is listed in logical rather than alphabetical order?

Is there any direct way to save into a new variable the frequencies obtained by applying the command tabulate?

6. Other

How do I identify neighbors of points or areas on a rectangular grid in Stata?

How do I identify leap years in Stata?

Why am I getting an error message that there is "insufficient disk space"?

How can I put the current date and time in my log files?

How do I accumulate the results of immediate commands?

Why does the command complain that there are no observations?

7. FAQs concerning Stata 11

Can I use ODBC to write to an existing Excel file?

Each morning I have to set my memory size to, say, 20m. The default, 1m, is not sufficient for my data. Is there a way of changing the default setting?

Why do I get the error message “no room to add more observations”?

How can I use a dataset that is larger than the available RAM?

8. FAQs concerning releases before Stata 11

How can I apply the original value and variable labels after using the reshape command?

Why does my merge produce a dataset with too many observations?

Is there a way to tell Stata to try all values of a particular variable in a for statement without specifying them?

How do I identify duplicate observations in my data?

How can I convert other packages' files to Stata format data files?

What do I do if the command I need cannot be used with by?

How do I create a variable that contains a repeating sequence of numbers?

I am having trouble converting a SAS dataset to a Stata dataset using Stat/Transfer. What is wrong?

What is the new reshape command?

Why does reshape give a too-many-variables error?

How do I create a lag variable?

How do I make date variables?

Why am I getting a message that there is no room on my hard drive?

FAQs
What's new?
Statistics
Data management

Graphics
Programming Stata
Mata
Resources
Internet capabilities
Stata for Windows
Stata for Unix
Stata for Mac
Technical support

Follow us

© Copyright 1996–2013 StataCorp LP | Terms of use | Privacy | Contact us | Site index | View mobile site