How to set environment variable using a data file in Postman

I have a data file having a column userid, now i want to set a environment variable based on the value of userid using pre-request script.

var i = data.userId;
console.log(i);

if(i==='1')
{
    pm.environment.set("id","i");
    //console.log(pm.environment.get("id"));
}

Can someone please help

I would have thought that you would need to adjust the script to something like this:

var i = pm.iterationData.get("userId");
console.log(i);

if( i === '1' )
{
    pm.environment.set("id", i);
   //console.log(pm.environment.get("id"));
}