Code Mismatch. Why?

[Annecy Houston]

Hello,

I have a variable, year, that has the year of birth of participants. I would like to create a new variable, age, that describes the age of each participant in 2023. I tried the following code: gen age=2023-year

I get a return of a mismatch error. Why and what would be the proper code to create my new variable?

Thanks in advance.

[Nick Cox]

I guess year is a string variable and the error message was type mismatch. If so,

destring year, replace

If not, or if that doesn't work, we need more details please: a data example and the exact error message(s) (don't paraphrase or rewrite).

[Annecy Houston]

gen age = 2023-year
type mismatch
r(109);
error . . . . . . . . . . . . . . . . . . . . . . . . Return code 109
type mismatch;
In an expression, you attempted to combine a string and numeric
subexpression in a logically impossible way. For instance, you
attempted to subtract a string from a number or you attempted
to take the substring of a number.

destring year, replace
year: contains nonnumeric characters; no replace

[Annecy Houston]

gen age = 2023-year
type mismatch
r(109);
error . . . . . . . . . . . . . . . . . . . . . . . . Return code 109
type mismatch;
In an expression, you attempted to combine a string and numeric
subexpression in a logically impossible way. For instance, you
attempted to subtract a string from a number or you attempted
to take the substring of a number.

destring year, replace
year: contains nonnumeric characters; no replace

*All year variables are numeric

[Clyde Schechter]

*All year variables are numeric

So you think. But Stata thinks otherwise. And I have never known Stata to get this kind of thing wrong. You just don't know your data as well as Stata does.

Run -describe year- and I'm willing to be it will show you that it's storage type is a string.

The fact that -destring- says year contains non-numeric characters tells you that, notwithstanding its name, the variable year contains extraneous material. Your task is to find it and fix it.

Run:

levelsof year if missing(real(year))

and you will get a listing of all the values of the year variable that contain non-numeric material. Depending on what that looks like, you will need to write and run some code to clean up that variable.

Caveat: It can happen that the output of the code that I have suggested you run will look like it has no non-numeric characters in it. That can happen if the contaminating material consists of non-printing characters. Those are characters that Stata can see but are not shown in listings and displays. If this happens to you, get Robert Picard's -chartab- command from SSC and run

chartab year

It will give you a complete listing, with explanations, and both decimal and hexadecimal character codes, of all the characters that appear in the variable. Reading the list you will easily find the non-numeric characters that are problematic, and then you can write your clean-up code.

[Annecy Houston]

Issue has been resolved.

[Clyde Schechter]

It would be nice if you would describe how you resolved the issue so that others who encounter a similar problem can learn from your experience.