Combining Three or More Categorical Variables Into One, But Keeping the Originals As They Are, Possible?

[Roman Johnson]

Hi,

I would like to combine three different categorical variables into one variable, keeping the original variables the same. I have heard of the egen command for this, but I am told this command works best for numerical variables. Which stata command would work best for what I wish to do? If you have recommendations, would you consider also placing the proper syntax here?

[Bruce Weaver]

Hello Roman. It will help a lot if you post a couple short data listings showing what the data look like now and what you want it to look like afterwards. See the FAQ for details on using -dataex-, code delimiters, etc. HTH.

[Nick Cox]

egen works fine here, contrary to misinformation.

https://www.stata-journal.com/sjpdf....iclenum=dm0034 is a miniature review.

As Bruce advises, do give a data example if you need more detailed help.

[Roman Johnson]

I would like this combine three variables: citizenp, geobrth, and yrsinus.

dataex citizenp yrsinus geobrth

----------------------- copy starting from the next line -----------------------

* Example generated by -dataex-. To install: ssc install dataex
clear
input byte(citizenp yrsinus geobrth)
2 3 3
2 4 3
1 5 3
1 5 2
1 5 3
2 4 3
2 5 3
2 5 3
2 2 3
2 3 3
1 5 3
2 5 3
1 5 3
1 5 2
1 5 2
2 4 3
2 5 3
1 3 3
2 5 3
2 5 3
2 4 3
2 5 3
2 5 3
1 5 3
1 5 3
2 4 3
2 5 3
2 5 3
1 5 2
2 5 3
1 5 3
2 4 3
2 5 3
2 5 3
2 2 3
2 2 3
1 5 3
1 5 3
2 4 3
2 4 3
2 4 3
1 5 3
1 5 3
1 5 3
1 5 3
2 4 3
1 5 3
1 3 3
1 5 3
2 4 3
2 5 3
1 5 3
1 5 3
2 5 3
2 3 3
2 2 3
2 3 3
2 5 3
1 5 3
2 3 3
2 5 3
1 5 3
1 5 3
2 5 3
1 5 3
1 5 3
2 5 3
1 3 3
1 5 3
1 4 3
1 5 3
2 5 3
2 5 3
2 4 3
1 4 3
1 4 2
2 2 3
2 4 3
1 5 3
1 5 3
2 5 3
1 5 3
1 5 3
1 4 3
1 5 3
1 5 3
2 5 3
2 3 3
1 5 3
1 5 3
2 5 3
2 4 3
1 5 3
2 5 3
2 5 3
1 3 2
1 5 3
1 5 3
2 5 3
1 5 2
end

------------------ copy up to and including the previous line ------------------

Listed 100 out of 1358 observations
Use the count() option to list more

I would like category 3 of geobrth, categories 3 4 5 of yrsinus, and 2 of citizenp combined into one new variable that I will name "naturalized". How would I do this?

[Nick Cox]

Is your combination

gen naturalized = (geobrth == 3) & inlist(yrsinus, 3, 4, 5) & (citizenp == 2) 

or should there be | instead of & there?

[Roman Johnson]

Yes, I believe so because I want each of those things to be true at once. Would I use the egen command instead of the gen command?

[Nick Cox]

If you want all conditions to be true, you need & as operator.

There is no choice here. egen doesn't support expressions of the kind in #5.

[Roman Johnson]

Thanks, Nick:

I see that I have two categories (0 & 1) that should all just represent those who are naturalized citizens. Is this correct?

dataex naturalized

----------------------- copy starting from the next line -----------------------

* Example generated by -dataex-. To install: ssc install dataex
clear
input float naturalized
1
1
0
0
0
1
1
1
0
1
0
1
0
0
0
1
1
0
1
1
1
1
1
0
0
1
1
1
0
1
0
1
1
1
0
0
0
0
1
1
1
0
0
0
0
1
0
0
0
1
1
0
0
1
1
0
1
1
0
1
1
0
0
1
0
0
1
0
0
0
0
1
1
1
0
0
0
1
0
0
1
0
0
0
0
0
1
1
0
0
1
1
0
1
1
0
0
0
1
0
end

------------------ copy up to and including the previous line ------------------

Listed 100 out of 1358 observations
Use the count() option to list more

.

[Bruce Weaver]

Hi Roman. If you used the code Nick gave in #5, variable naturalized = 1 for each subject who meets all 3 conditions, and naturalized = 0 for subjects who do not meet all 3 conditions. HTH.

[Roman Johnson]

Thank you, Bruce.