Drop if - variable not found

[Hidde van Lent]

Hi all,

Just a very simple question and command yet I can't figure out why it is not working.

I just downloaded a dataset on all company's in the North-American market. Now I simply want to get rid of the American companies to see whether all cross-listed companies have a foreign primary issue tag. Therefore, as a first command (after clear all, cd and sysuse) I run:
drop if fic==USA
And then it says:
USA not found

It does not work for any of the -fic- or -tic- commands, but if I for instance do the command:
drop if fyear==2002
Then it does drop the years 2002

How is this possible and how can I resolve this? Thanks in advance for your help.

[Nick Cox]

drop if fic == "USA"

Otherwise Stata is looking for a variable named USA, which you do not have. That's what Stata is telling you.

[Hidde van Lent]

I thought I already tried all of these, but I only tried either with apostrophes or with spaces, not combined. Thank you Nick!
Good to know that without spaces and brackets it reads it as a variable - this does explain why it did drop the whole variable fic if I typed it in the same format.

[Jorrit Gosens]

The difference is in the quotation marks only.
Compare:

webuse grunfeld, clear
tostring company, replace
drop if company=="2"

Drops obs where company has the value "2"

webuse grunfeld, clear
drop if company==time

Drops obs where the variable company has the same value as the variable time

[Hidde van Lent]

Yes I just noticed it. instead of " I used ' so that was the mistake I made. Thanks again.