Re: st: looping over a variable list of variables

[Nick Cox <njcoxstata@gmail.com>]

Using -egen-'s -group()- function in every case might help.

In Stata local macros are not regarded as variables.

Nick

On 23 Nov 2012, at 18:28, Pradipto Banerjee <pradipto.banerjee@adainvestments.com 
> wrote:

> Hi,
>
> Suppose I have a set of variables v1, v2, v3, ..., vn where each  
> variable takes a value equal to 0, 1, 2. I want to write a program  
> that can do the following:
>
> 1. If the program is supplied with v1, then it loops over v1 = 0, 1,  
> 2 and does some operation for each value of v1 . Here I can achieve  
> it with a single - forvalues - loop
>
> 2. If the program is supplied with v1 & v2, then it loops over v1 =  
> 0,1,2 and v2=0,1,2 (i.e. a total of 9 loops), and does some  
> operation for each combination of v1 & v2. Here I can achieve it  
> with two nested -forvalues- loops
>
> 3. Similarly, if v1, v2, v3 are supplied, I can achieve it with  
> three nested -forvalues- loops
>
> The problem can get out of hand if v1, v2, v3, ..., vn is supplied  
> to the program as I need to hard-code the nested loops structures up  
> to a large value of n.
>
> An alternative is to run one - forvalues - or -forvalues- loop with  
> all permutations of v1, v2, v3,..., vn already determined in a local  
> macro variable.
>
> Is there way / function that can return all permutations of v1, v2,  
> v3 ..., vn in a local macro variable(s) ?
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