Re: st: How to check if observation of a particular variable value exists? If not, create that observation.

[Phil Clayton <philclayton@internode.on.net>]

Here's a tweak of your existing code:

forvalues i = 1/2 {
 forvalues j = 1/2 {
   count if A == `i' & B == `j'
   if r(N)==0 {
     set obs `=_N+1'
     replace A = `i' in `=_N'
     replace B = `j' in `=_N'
   }
 }
}

Phil

On 29/05/2012, at 7:09 PM, Ran Gu wrote:

> Dear Statalisters:
> 
> Good day. I hope you can help me with the following question.
> 
> Suppose I have a data with 2 variables, say A and B, both with values
> 1 and 2. The data are sorted by A and B. Then there should be 4
> records: (A=1 B=1) (A=1 B=2) (A=2 B=1) (A=2 B=2)
> 
> Suppose I don't know whether the 4 observations are all exist or not.
> How could I check that in a do file?
> Then, If a record is missing, say (A=1 B=1), I would like to create it.
> 
> for example:
> forvalues i = 1/2 {
>  forvalues j = 1/2 {
>    if obs with A == `i' and B == `j' is missing {
>      local new = _N+1
>      set obs `new'
>      replace A == `i' if _n==`new'
>      replace B == `j' if _n==`new'
>    }
>  }
> }
> 
> 
> -- 
> All the best,
> Ran
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