Mandy wrote:
Could anyone could give me some hint on how to delete all the
observations with missing values for at least one variable? I know it's
a quite simple question. But I havn't figured out a good way to deal
with this.
Here's an example to show this:
----------------------------------------------------------
ID var1 var2 var3
1 0 2 1
2 -2 1 3
3 0 -4 9
4 1 0 1
---------------------------------------------------------
What I want to do is to drop observation whose ID is 2 and 3.
If there are not many variables in the data set, I know I could do:
. drop if var1<0| var2<0 | var3<0
But this way is inconvenient if there are a lot of variables (like 50
variables) in the data set.
--------------------------------------------------------------------------------
Martin Weiss has already shown an approach using -egen-.
Another approach is to use -foreach- to loop across variables.
foreach var of varlist var1-var50 {
drop if `var' < 0
}
Various convenient shortcuts are available in Stata for specifying lists
of variables, such as
foreach var of varlist var?? {
. . .
}
foreach var of varlist v* {
. . .
}
foreach var of varlist _all {
. . .
}
I recommend reading the help files and hardcopy documentation on looping in
Stata (-foreach- and -forvalues-) and on how lists of variables (-varlist-)
are handled in Stata, including the use of "wildcards".
Joseph Coveney
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