I know a way of finding and identifying missing values for a particular variable.
For the variable avedmajor, I could do
tab avedmajor, m
Then,
gen avedmajormissing=0
replace avedmajormissing=1 if avedmajor==.
But how to see if my dataset has missing values in any of the variables without going through each one of them?
Thanks.
I'd add mdesc command to proposed solutions. According to description mdesc:
Produces a table with the number of missing values, total number of cases, and percent missing for each variable in varlist. mdesc works with both numeric and character variables.
So advantage to misstable solution is that it works with both numeric and string variables in one go.
sysuse auto
mdesc
Gives a nice overview of missings:
Variable | Missing Total Percent Missing
----------------+-----------------------------------------------
make | 0 74 0.00
price | 0 74 0.00
mpg | 0 74 0.00
rep78 | 5 74 6.76
headroom | 0 74 0.00
trunk | 0 74 0.00
weight | 0 74 0.00
length | 0 74 0.00
turn | 0 74 0.00
displacement | 0 74 0.00
gear_ratio | 0 74 0.00
foreign | 0 74 0.00
----------------+-----------------------------------------------
One command is:
misstable summarize
But see also:
help missing##useful
and more generally:
help missing
Another option would be misschk from the SPost site. Type findit misschk to install it. Here's an example:
sysuse auto,clear
replace price=. if (_n==1|_n==3) // additional missing values
misschk
Without specifying the varlist, misschk just checks all variables.
The standard output gives you the number as well as percentage of missing values on each variable.
Variables examined for missing values
# Variable # Missing % Missing
--------------------------------------------
1 price 2 2.7
2 mpg 0 0.0
3 rep78 5 6.8
4 headroom 0 0.0
5 trunk 0 0.0
6 weight 0 0.0
7 length 0 0.0
8 turn 0 0.0
9 displacement 0 0.0
10 gear_ratio 0 0.0
11 foreign 0 0.0
It also counts all the different missing patterns.
Missing for |
which |
variables? | Freq. Percent Cum.
---------------+-----------------------------------
1_3__ _____ _ | 1 1.35 1.35
1____ _____ _ | 1 1.35 2.70
__3__ _____ _ | 4 5.41 8.11
_____ _____ _ | 68 91.89 100.00
---------------+-----------------------------------
Total | 74 100.00
Lastly, it summarizes the amount of missing values by cases.
Missing for |
how many |
variables? | Freq. Percent Cum.
------------+-----------------------------------
0 | 68 91.89 91.89
1 | 5 6.76 98.65
2 | 1 1.35 100.00
------------+-----------------------------------
Total | 74 100.00
misschk also has a couple of other neat features with additional options you can find out about with help misschk.
missings from the Stata Journal offers a bundle of subcommands.
search dm0085 will yield a clickable link to the latest version of the file.
The write-up in the Stata Journal will emerge from behind a paywall on the publication of Stata Journal 18(4) in December 2018 or January 2019.
Before then, or even after, the examples in the Statalist announcement give much flavour.
Here is a token:
. webuse nlswork, clear
(National Longitudinal Survey. Young Women 14-26 years of age in 1968)
. missings report
Checking missings in all variables:
15082 observations with missing values
age 24
msp 16
nev_mar 16
grade 2
not_smsa 8
c_city 8
south 8
ind_code 341
occ_code 121
union 9296
wks_ue 5704
tenure 433
hours 67
wks_work 703
. missings report, min(1000)
Checking missings in all variables:
15082 observations with missing values
union 9296
wks_ue 5704
This command is considered to supersede nmissing.
ORIGINAL POST BELOW July 9 2014
Various commands help. See e.g. codebook. For one user-written command, install nmissing.
. search nmissing, historical
Search of official help files, FAQs, Examples, SJs, and STBs
FAQ . . . . . . Can I quickly see how many missing values a variable has?
. . . . . . . . . . . . . . . . . . UCLA Academic Technology Services
7/08 http://www.ats.ucla.edu/stat/stata/faq/nmissing.htm
Example . . . . . . . . . . . . . . . . . . . . Useful non-UCLA Stata programs
. . . . . . . . . . . . . . . . . . UCLA Academic Technology Services
7/08 http://www.ats.ucla.edu/stat/ado/world/
SJ-5-4 dm67_3 . . . . . . . . . . Software update for nmissing and npresent
(help nmissing if installed) . . . . . . . . . . . . . . . N. J. Cox
Q4/05 SJ 5(4):607
now produces saved results
SJ-3-4 sg67_2 . . . . . . . . . . Software update for nmissing and npresent
(help nmissing, npresent if installed) . . . . . . . . . . N. J. Cox
Q4/03 SJ 3(4):449
updated to include support for by, options for checking
string values that contain spaces or periods, documentation
of extended missing values .a to .z, and improved output
STB-60 dm67.1 . . . . Enhancements to numbers of missing and present values
(help nmissing if installed) . . . . . . . . . . . . . . . N. J. Cox
3/01 pp.2--3; STB Reprints Vol 10, pp.7--9
updated with option for reporting on observations
STB-49 dm67 . . . . . . . . . . . . . Numbers of missing and present values
(help nmissing if installed) . . . . . . . . . . . . . . . N. J. Cox
5/99 pp.7--8; STB Reprints Vol 9, pp.26--27
commands to list the numbers of missing values and nonmissing
values in each variable in varlist
Here is an example:
. webuse nlswork
(National Longitudinal Survey. Young Women 14-26 years of age in 1968)
. nmissing
age 24
msp 16
nev_mar 16
grade 2
not_smsa 8
c_city 8
south 8
ind_code 341
occ_code 121
union 9296
wks_ue 5704
tenure 433
hours 67
wks_work 703
gen avedmajormissing = missing(avedmajor). Note also that your syntax does nothing about extended missing values and is only for numeric variables.