How to shorten multiple line of codes relevant?

[Phuc Nguyen]

In my data, I have a numeric number called year which have value from 2 to 22, I want to replace this variable by a variable year1 which have the value from 2001 to 2021.
For sure the very clear way to do is:

gen year1=.
replace year1=2001 if (year==2)
replace year1=2002 if (year==3)
.replace year1=2003 if (year==4)
.
.
.
(similar code)

However, it is around 21 lines of code and it is not necessarily like that from my point of view. I have a look at some ways to shorten it. For example, by using the semicolon delimiter as mentioned in this archive.
My code is

replace year1=2001 if (year==2); replace year1=2002 if (year==3)

However, it turns out the error like that

unknown function ()
r(133);

Could you please help me to sort it out?Thanks in advance

[Clyde Schechter]

It's just one line:

gen year1 == 1999+year

[Hemanshu Kumar]

The specific code you have is replaced perfectly by the line provided in #2. If you had other code where you wanted to use the semi-colon, you would need to get Stata to change the delimiter, a bit like this:

#delimit ;

command 1 ; command 2 ; command 3;

very long
command
spread over
many lines ;

#delimit cr

The main use of this feature is actually not to shorten the command; it is largely used when you want to split up a very long command that is hard to read on one line (and/or you find it painful to split it up using three forward slashes /// ).

[Phuc Nguyen]

It's just one line:

gen year1 == 1999+year

Thanks Clyde Schechter , However, when I typed the command suggested

gen year1 == 1999+year

It showed that

== invalid name
r(198);

Could you please kindly to help me in sorting it out?

[Phuc Nguyen]

I sorted it already, we have one redundant "=". The code should be:

g

en year1=1999+year

[Clyde Schechter]

Yes, sorry for that typo.