Generate var named after the first character of element in loop

[Liz Broom]

Hi, I have written code to iteratively use a list of dta files. Now I want to generate a var which is named according to the first character of the dta file.

Here is my current code, where the var is named according to the entire file name:

foreach file in afile bfile cfile {
gen `file' = x_var
}

I want to generate a var in each file, e.g. afile.dta would contain the var: a_var

I have tried adding a line before the gen line to generate a local which displays the first letter of the element, but I'm not sure what command to use to do so as substr is not allowed (see below). Perhaps a command like word but for single characters?

foreach file in afile bfile cfile {
local shorthand di : substr("`fluid'", 1, 1)
gen `file' = `shorthand'_var
}

substr not allowed

I'd be very grateful if somebody could advise on the command!

Many thanks,
Liz

[Andrew Musau]

I want to generate a var in each file, e.g. afile.dta would contain the var: a_var

You need to load the dataset first, which I do not see you doing in your code.

foreach file in afile bfile cfile {
    use `file', clear
    gen `file'= `=substr("`file'", 1, 1)'_var
    save `file', replace
}

The above assumes that in the file afile.dta, there is a variable named a_var. Thus, you generate a variable named afile in this file that is equal to a_var.

[Liz Broom]

Hi Andrew, thanks so much for your reply!

Sorry, I accidentally mixed things up in the code when I was simplifying it to write here and so I haven't conveyed my question very clearly - I am actually trying to name the var after the first letter, rather than specifying the value of the var I generate. For example, file afile would have a var named a_var which would have a value of 1 for every observation in the code below.

The code in the original question should have read as follows:

foreach file in afile bfile cfile {
use `file', clear
local shorthand di : substr("`file'", 1, 1)
gen `shorthand'_var = 1
}

This generates the error:

( invalid name

Here is the code with your correction to the substr comand:

foreach file in afile bfile cfile {
use `file', clear
local shorthand di : "`=substr("`file'", 1, 1)'_var"
gen `shorthand' = 1
}

This generates a var named di with the value of 1 for each observation. I want the var name to be x_var, where x is the first character of the file name.

Apologies again for making such a mess of the question the first time, and thanks again!

Best,
Liz

[Andrew Musau]

foreach file in afile bfile cfile {
    use `file', clear
    gen `=substr("`file'", 1, 1)'_var=1
    save `file', replace
}

[Liz Broom]

Ah amazing, thank you! A very simple fix

[Liz Broom]

Apologies to keep asking on this thread, but is there a way I can save that code as a local so that I can easily use it whilst generating lots of different var, all of which I want to contain the corresponding file character within the middle of the var name. I have tried doing so as follows, but this just generates a var named 'example__example' with the value of 1:

foreach file in afile bfile cfile {
use `file', clear
local shorthand "`=substr("`file'", 1, 1)'"
gen example_`shorthand'_example = 1
save `file', replace
}

Many thanks,
Liz

[Andrew Musau]

Drop the double quotes:

foreach file in afile bfile cfile {
    use `file', clear
    local shorthand = substr("`file'", 1, 1)
    gen example_`shorthand'_example = 1
    save `file', replace
}

[Liz Broom]

Thank you Andrew!