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| = Stata Aggregating Data = | = Aggregating Data with Stata = Stata offers several commands for computing aggregated statistics and translating datasets into aggregated formats. |
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| == Contract == | == Statistics == |
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| The '''`collapse`''' command is ideal for aggregated statistics. | The [[Stata/Summarize|-summarize-]] command computes and [[Stata/StoredResults|stores]] descriptive statistics. The [[Stata/Inspect|-inspect-]] command is useful for interactive exploration. The [[Stata/Contract|-contract-]] and [[Stata/Collapse|-collapse-]] commands create datasets of aggregated statistics. The former is useful for descriptive statistics, while the latter is designed for summary statistics. |
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| contract VAR, freq(Count) percent(Percentage) | contract foo, freq(Count) percent(Percentage) |
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| == Collapse == | == Wide and Long Data == |
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| ---- | The [[Stata/Reshape|-reshape-]] command can be used to translate datasets between wide and long formats. |
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== Reshape == The '''`reshape`''' command can be used to move data between wide and tall formats. It has additional, helpful features, such as a diagnostic `reshape errors` command. === Reshape Wide === To expand long data into a wide format, try: |
To translate into a wide format, try: |
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| If the group indicator should be placed anywhere other than as a suffix to `VARSTUB`, use a single at siogn (`@`) to indicate the placement. For example, if the groups are `1`, `2`, and `3`, then the command `reshape wide inc@r, i(KEYVAR) j(GROUPVAR)` would create variable `inc1r`, `inc2r`, and `inc3r`. If `GROUPVAR` is a string variable, the `string` option is mandatory. If data has been transformed through a `reshape wide` command like above, then to restore data to the long format, try: {{{ reshape long }}} The parameters of the transformation are stored and reused between calls. === Reshape Long === To contract wide data into a long format, try: |
To translate into a long format, try: |
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| ...`VARSTUB` will be created from the variable list `VARSTUB*`, and `GROUPVAR` will be created to indicate the source of `VARSTUB`. If the `string` option is specified, `GROUPVAR` will be a string variable. If the variable list does not follow the simple pattern of `VARSTUB*`, it may be possible to specify with an at sign (`@`). For example, if the target variables are `inc1r`, `inc2r`, and `inc3r` and the intended `GROUPVAR` groups are `1`, `2`, and `3`, then the command `reshape long inc@r, i(KEYVAR) j(GROUPVAR)` would correctly create the variable `incr`. If data has been transformed through a `reshape long` command like above, then to restore data to the wide format, try: {{{ reshape wide }}} The parameters of the transformation are stored and reused between calls. |
The variable `VARSTUB` will be created from the variable list `VARSTUB*`, and `GROUPVAR` will be created to indicate the source of `VARSTUB`. |
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.