Let’s walk through a solid foreach-based solution to rename your binary variables—this will reliably swap out the onsite_ prefix for q0052_ without the headaches you ran into with substr. I’ll focus on Stata since that’s the environment where this workflow is most common, but the core logic applies to other languages like R or Python with small adjustments.

Step 1: Identify Target Variables #

First, we’ll grab all variables that start with onsite_ and store them in a local macro. This ensures we only work with the variables we care about:

* Store all onsite_* variables in a local macro
ds onsite_*
local target_vars `r(varlist)'

Step 2: Loop Through and Rename Each Variable #

Use foreach to iterate over every variable in our list. For each one, we’ll strip off the onsite_ prefix, then append it to the new q0052_ prefix. We’ll use subinstr here because it’s more robust than substr (no need to count exact character positions—great if you ever have prefixes of varying lengths later):

* Loop through each target variable
foreach var of local target_vars {
    * Extract the part after "onsite_"
    local suffix = subinstr("`var'", "onsite_", "", .)
    * Rename the variable with the new prefix
    rename `var' q0052_`suffix'
    * Optional: Print progress to verify
    di "Renamed `var' to q0052_`suffix'"
}

Why substr Might Have Failed #

If you tried substr before and it didn’t work, it’s likely because you miscalculated the starting position. For onsite_ (which is 7 characters long), you’d need to start at position 8:

* Alternative with substr (only works if prefix length is fixed)
local suffix = substr("`var'", 8, .)

But subinstr is safer because it doesn’t depend on counting characters—if your prefix ever changes (e.g., onsite_service_ instead of onsite_), you just update the search string instead of recalculating positions.

Bonus: Handle Multiple Prefixes (If Needed) #

If you have other prefixes to swap (e.g., remote_ variables that need q0053_), you can expand the logic with a nested loop or conditional checks inside the foreach:

* Example for multiple prefix-pairs
local prefix_pairs "onsite_ q0052_ remote_ q0053_"
foreach pair of local prefix_pairs {
    gettoken old_prefix new_prefix : pair
    ds `old_prefix'*
    local vars `r(varlist)'
    foreach var of local vars {
        local suffix = subinstr("`var'", "`old_prefix'", "", .)
        rename `var' `new_prefix'`suffix'
    }
}

内容的提问来源于stack exchange，提问作者seder163