if two string variables are different

[Alex Potter]

Hi,

I have variables "Dummy", "ctry1" and "ctry2" and expect to get "DifferentDummy" (table like below).

Dummy	ctry1	ctry2	DifferentDummy
0	FR	FR	0
0	FR	IE	0
1	FR	FR	0
1	FR	IE	1

If Dummy=1, and "ctry1" does not equal "ctry2", then DifferentDummy=1,

I used the following code,

gen DifferentDummy =0
replace DifferentDummy =1 if (Dummy ==1) & ("`ctry1'"!=="` ctry2'")

but failed(get the table likes below),

Dummy	ctry1	ctry2	DifferentDummy
0	FR	FR	0
0	FR	IE	0
1	FR	FR	1
1	FR	IE	1

Could you please give me some advice about this？
Many thanks in advance.

[Nick Cox]

gen DifferentDummy = (Dummy == 1) & (ctry1 != ctry2)

There were two mistakes, using !== and using local macros where variable names give you a direct solution.

See also

https://www.stata.com/support/faqs/d...rue-and-false/

https://www.stata-journal.com/articl...article=dm0099

for more on why

generate wanted = true or false condition

helps you avoid that awkward two-step.

[Alex Potter]

Hi Nick Cox , Many thanks for your reply, it is a great help.