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# Re: st: If variable x contains variable y

 From Christoph Engel <[email protected]> To [email protected] Subject Re: st: If variable x contains variable y Date Sun, 15 Jul 2012 17:20:32 +0200

```John,

```
You will have to define the value of x if y does not fulfil your condition, i.e. if it is not equal to z. Depending on your purposes you might either want it to be a missing value, or some expression of x, say 0. I would therefore start out
```
gen x = .
replace x = y if y == z

(note the "==" in the if clause)

Best

Christoph Engel

Am 7/15/2012 4:59 PM, schrieb Steve Nakoneshny:
```
```John,

At first glance, it would seem that -gen x = y if y = z- would serve as a solution. Of course, this assumes that your I'd vars are numerical and not string vars (which they probably should be stored as).

Steve

Sent via carrier pigeon

On 2012-07-15, at 8:52 AM, "[email protected]"<[email protected]>  wrote:

```
```Hello,

This is my first time using statalist, I hope I do this all correctly!

I'm looking to create a variable x which is equal to y, but only if the given value for y can be found in another variable, z. These are all id numbers, so say y is a universal id and z is a mother's id, telling you the universal id of the mother in relation to the child.

For example:

yzx

1..
2.2
3.3
42.
5..
6..
737
8..
9..
107.

So I'm trying to figure out how to create x. Any help would be much appreciated.

Thanks,
John

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```

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_________________________________________________________________
Prof. Dr. Christoph Engel
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