Aggregating Data with Stata
Stata offers several commands for computing aggregated statistics and translating datasets into aggregated formats.
Statistics
The -summarize- command computes and stores descriptive statistics.
The -inspect- command is useful for interactive exploration.
The -contract- and -collapse- commands create datasets of aggregated statistics. The former is useful for descriptive statistics, while the latter is designed for summary statistics.
contract foo, freq(Count) percent(Percentage)
Wide and Long Data
The -reshape- command can be used to translate datasets between wide and long formats.
To translate into a wide format, try:
reshape wide VARSTUB, i(KEYVAR) j(GROUPVAR)
A series of variables named like VARSTUB* will be created, for each group of GROUPVAR.
To translate into a long format, try:
reshape long VARSTUB, i(KEYVAR) j(GROUPVAR)
The variable VARSTUB will be created from the variable list VARSTUB*, and GROUPVAR will be created to indicate the source of VARSTUB.