Looping over many names which don't have rules

Question

When there are just few names, looping in Stata is easy.

Also, when there is a rule as to how the names change (e.g. increment) I can do the following:

forval i = 1/5 {
    ...
}

However, there are cases where i have hundreds of names that I need to loop over, which don't have rules of increment.

For example:

48700 48900 48999 49020 49180 49340 ...

Is there some short-hand way of writing the loop? Or do I just have to painstakingly list all of them?

Answer 1

The answer is it depends.

If these are part of variable names, you can do something like this:

clear
set obs 5

foreach var in 48700 48900 48999 49020 49180 49340 {
    generate var`var' = runiform()
}

ds
var48700  var48900  var48999  var49020  var49180  var49340

ds var48*
var48700  var48900  var48999

local names `r(varlist)'

foreach var of local names {
    display `var'
}

.41988069
.06420179
.36276805

If these are file names, a macro extended function can be handy:

dir, w

48700.rtf       48999.rtf       49180.rtf
48900.rtf       49020.rtf       49340.rtf

local list : dir . files "*"
display `list'
48700.rtf48900.rtf48999.rtf49020.rtf49180.rtf49340.rtf

local list : dir . files "48*"
display `list'
48700.rtf48900.rtf48999.rtf

foreach fil of local list {
    display "`fil'"
}
48700.rtf
48900.rtf
48999.rtf

EDIT:

The above approaches are concerned with how to efficiently get all relevant names in a local macro.

If you already know the names and you merely want a cleaner way to write the loop (or want to re-use the names in several loops), you can simply assign these in a local macro yourself:

local names var48700 var48900 var48999 var49020 var49180 var49340

foreach var of local names {
    display `var'
}

.41988069
.06420179
.36276805
.52763051
.16493952
.66403782

The local macro names will automatically expand during run time to include all the specified items.