Adding suffix or prefix to each element of a global varlist

[Roberto Musmeci]

Hello,

I have a core set of variables and for each of them I generated several secondary variables. To keep my codes clean and short, I would like to define a global containing my core variables and then simply attach the relevant prefix or suffix.

My suffix is "_OP" and I would like to attach it to all the elements of the global list1

global list1 "x1 x2 x3 "
tabstat ${list1}_OP, s(co me p50 min max v) columns(statistics) save

Not sursprisingly, when running the code, Stata display "x1 ambigous abbreviation"

Thank you very much in advance for your help.

[Nick Cox]

On the evidence you give, this might work:

tabstat x?_OP

with options to suit.

General advice is to avoid the use of globals, as likely to be a source of bugs. I think it's several years since I defined any at all and I use Stata almost every day.

[Roberto Musmeci]

Hi Nick

Thank you for your message.

Unfortunately the variables are called differently than the `x' I used in the example.
In the end, I have used a foreach loop with a subinstr function to solve the issue. However, I will keep in mind your suggestion and warning about the bugs.

Code:
foreach x of global list1{
global `x'_OP : subinstr global `x' " " " OP_", all

[Castor Comploj]

Roberto Musmeci Did you find a solution to this problem? Was this the best solution?

[Clyde Schechter]

Endorsing Nick's advice in #2 to avoid globals, here's how to do it with a local macro:

local list1 x1 y2 abracadabra
display `"`list1'"'

local list1_OP: subinstr local list1 " " "_OP ", all
local list1_OP `list1_OP'_OP
display `"`list1_OP'"'

If you really need to use a global macro instead, the code is almost the same. Substitute global for local and using $, with {} where needed, rather than `' for dereferencing. But, really, don't use a global unless there is no alternative. I've been using Stata pretty much daily since 1994 and only once found it necessary to resort to a global. (Even then, in retrospect, there were better alternatives, although a local would not have worked in that situation.)