silencezou 发表于 2015-4-9 14:37 
您好！请问对于出现repeated time values时且有大量数据（如几十万个obs），无法手动检查的情况，有什么程 ...
Title
[D] duplicates -- Report, tag, or drop duplicate observations
Syntax
Report duplicates
duplicates report [varlist] [if] [in]
List one example for each group of duplicates
duplicates examples [varlist] [if] [in] [, options]
List all duplicates
duplicates list [varlist] [if] [in] [, options]
Tag duplicates
duplicates tag [varlist] [if] [in] , generate(newvar)
Drop duplicates
duplicates drop [if] [in]
duplicates drop varlist [if] [in] , force
options Description
----------------------------------------------------------------------------------------------------------
Main
compress compress width of columns in both table and display formats
nocompress use display format of each variable
fast synonym for nocompress; no delay in output of large datasets
abbreviate(#) abbreviate variable names to # characters; default is ab(8)
string(#) truncate string variables to # characters; default is string(10)
Options
table force table format
display force display format
header display variable header once; default is table mode
noheader suppress variable header
header(#) display variable header every # lines
clean force table format with no divider or separator lines
divider draw divider lines between columns
separator(#) draw a separator line every # lines; default is separator(5)
sepby(varlist) draw a separator line whenever varlist values change
nolabel display numeric codes rather than label values
Summary
mean[(varlist)] add line reporting the mean for each of the (specified) variables
sum[(varlist)] add line reporting the sum for each of the (specified) variables
N[(varlist)] add line reporting the number of nonmissing values for each of the (specified)
variables
labvar(varname) substitute Mean, Sum, or N for varname in last row of table
Advanced
constant[(varlist)] separate and list variables that are constant only once
notrim suppress string trimming
absolute display overall observation numbers when using by varlist:
nodotz display numerical values equal to .z as field of blanks
subvarname substitute characteristic for variable name in header
linesize(#) columns per line; default is linesize(79)
----------------------------------------------------------------------------------------------------------
Menu
Data > Data utilities > Manage duplicate observations
Description
duplicates reports, displays, lists, tags, or drops duplicate observations, depending on the subcommand
specified. Duplicates are observations with identical values either on all variables if no varlist is
specified or on a specified varlist.
duplicates report produces a table showing observations that occur as one or more copies and indicating
how many observations are "surplus" in the sense that they are the second (third, ...) copy of the first
of each group of duplicates.
duplicates examples lists one example for each group of duplicated observations. Each example represents
the first occurrence of each group in the dataset.
duplicates list lists all duplicated observations.
duplicates tag generates a variable representing the number of duplicates for each observation. This will
be 0 for all unique observations.
duplicates drop drops all but the first occurrence of each group of duplicated observations. The word
drop may not be abbreviated.
Any observations that do not satisfy specified if and/or in conditions are ignored when you use report,
examples, list, or drop. The variable created by tag will have missing values for such observations.
Options for duplicates examples and duplicates list
+------+
----+ Main +----------------------------------------------------------------------------------------------
compress, nocompress, fast, abbreviate(#), string(#); see [D] list.
+---------+
----+ Options +-------------------------------------------------------------------------------------------
table, display, header, noheader, header(#), clean, divider, separator(#), sepby(varlist), nolabel; see
[D] list.
+---------+
----+ Summary +-------------------------------------------------------------------------------------------
mean[(varlist)], sum[(varlist)], N[(varlist)], labvar(varname); see [D] list.
+----------+
----+ Advanced +------------------------------------------------------------------------------------------
constant[(varlist)], notrim, absolute, nodotz, subvarname, linesize(#); see [D] list.
Option for duplicates tag
generate(newvar) is required and specifies the name of a new variable that will tag duplicates.
Option for duplicates drop
force specifies that observations duplicated with respect to a named varlist be dropped. The force option
is required when such a varlist is given as a reminder that information may be lost by dropping
observations, given that those observations may differ on any variable not included in varlist.
Remarks
As of Stata 11, the browse subcommand is no longer available. To open duplicates in the Data Browser, use
the following commands:
. duplicates tag, generate(newvar)
. browse if newvar > 0
See [D] edit for details on the browse command.
Examples
Setup
. sysuse auto
. keep make price mpg rep78 foreign
. expand 2 in 1/2
Report duplicates
. duplicates report
List one example for each group of duplicated observations
. duplicates examples
List all duplicated observations
. duplicates list
Create variable dup containing the number of duplicates (0 if observation is unique)
. duplicates tag, generate(dup)
List the duplicated observations
. list if dup==1
Drop all but the first occurrence of each group of duplicated observations
. duplicates drop
List all duplicated observations
. duplicates list
但对stata的数据结构不是很明白，所以问题多多。
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