type mismatch r(109);

[Lucian Lipciuc]

Hello
I'm trying to drop the observations that have no national ID number (nino) and I'm using "drop if nino == ." command.
Unfortunately is not working saying " type mismatch r(109); "
Can someone help me?
Thanks

[Carlo Lazzaro]

Lucian:
welcome to this forum.
Is -nino- in -string- format?
If that were the case, you should modify your code as follows:

drop if nino==""

[Lucian Lipciuc]

Hi, I don't know what is string format but is worked :o

[Carlo Lazzaro]

Lucian:

. use "C:\Program Files (x86)\Stata15\ado\base\a\auto.dta"
(1978 Automobile Data)

. list make price in 1

     +---------------------+
     | make          price |
     |---------------------|
  1. | AMC Concord   4,099 |
     +---------------------+

.

-make- is -string-; -price- is numeric.

See -help format-.

[Nick Cox]

Let me amplify the helpful replies by Carlo Lazzaro :

Format is an overloaded word in computing.

It can mean file format; data format (often better called structure or layout); variable or storage type; and display format. And very likely it has other meanings too that I have forgotten or never knew.

In Stata (all else can suit itself) there are string display formats associated with string variables which hold text or character strings.

A type mismatch is this: you are asking for something to be done that applies to a numeric variable or entity, but what you have is a string; or vice versa. It's like trying to fit a square toy into a round hole, or a round toy into a square hole.