Use foreach to iterate over each variable and rename it based on value in first and second row

[Carl Isaac]

I am fairly new to Stata, but I am used to Python and R where something like this seems easier to do. Basically, I want to iterate over each variable and rename it the value of its first and second row. For example, if the data looked like this:

A1	A2	A3	A4	...
C99	C92	C91	C30	...
J	J	K	K

I want to transform it to this:

C99J	C92J	C91K	C30K
C99	C92	C91	C30	...
J	J	K	K	...

So far, I have a loop that looks like so:

unab varlist : *
foreach i of loc varlist {
display `i'[1]
}

Which displays the value of each first row. I am confused on how you rename based on those values though. If I try the following to just name it by the first row:

unab varlist : *
foreach i of loc varlist {
rename `i' `i'[1]
}

It does not appear to work. Any help would be greatly appreciated!

[Justin Niakamal]

Welcome to Statalist. Perhaps something like this

clear
input str3(A1 A2 A3 A4)
"C99" "C92" "C91" "C30"
"J"   "J"   "K"   "K"  
end

foreach v of varlist _all {
    ren `v' `=`v'[1] + `v'[2]'
}

Result

  +---------------------------+
  | C99J   C92J   C91K   C30K |
  |---------------------------|
  |  C99    C92    C91    C30 |
  |    J      J      K      K |
  +---------------------------+

[daniel klein]

This problem is better solved at the stage of importing the data in Stata. Otherwise, the next question will probably be how to transform string variables into numeric ones... The answer to this is probably destring by the way.

[Joro Kolev]

It is pretty much what Justin did.

But I have an existential question to ask Carl Isaac. When "but I am used to Python and R where something like this seems easier to do", why dont you just do it in Python or R?

[Carl Isaac]

What Justin did does not seem to work for me. I ended up getting:

syntax error
Syntax is
rename oldname newname [, renumber[(#)] addnumber[(#)] sort ...]
rename (oldnames) (newnames) [, renumber[(#)] addnumber[(#)] sort ...]
rename oldnames , {upper|lower|proper}

Joro, I have decided to start learning Stata in more depth since it is commonly used in the econ community. That way I have the ability to work on the same code with colleagues.

[Andrew Musau]

For future reference, please copy and paste your exact command and the resulting Stata output. Most probably, your error results from spaces within strings, e.g., C 32 instead of C32. Stata variable names cannot contain spaces or characters other than letters, numbers and underscores. In addition, they cannot begin with numbers. The function -strtoname()- may help here, see

help strtoname()

foreach v of varlist _all {
    ren `v' `=strtoname(`v'[1] + `v'[2])'
}

[Joro Kolev]

Good luck with learning Stata then !

Justin's code is fine and it should work. Most likely it is what Andrew says in #6.

But if you try what Andrew suggested and still it does not work, do

set trace on

then run the code. Look up to the message in red which is saying exactly where and why the error occurred. Then copy and paste here say 7 lines before and 5 lines after the message in red.

What Justin did does not seem to work for me. I ended up getting:

syntax error
Syntax is
rename oldname newname [, renumber[(#)] addnumber[(#)] sort ...]
rename (oldnames) (newnames) [, renumber[(#)] addnumber[(#)] sort ...]
rename oldnames , {upper|lower|proper}

Joro, I have decided to start learning Stata in more depth since it is commonly used in the econ community. That way I have the ability to work on the same code with colleagues.