# Re: st: Using gen / egen in one step (not two)

 From "Jeremy Miles" <[email protected]> To [email protected] Subject Re: st: Using gen / egen in one step (not two) Date Sun, 7 Jan 2007 10:38:32 -0800

```Hi Nick

Thanks for that - it makes sense, when you put it like that, although
it's a pretty subtle distinction in the manuals [-gen- uses =exp ;
-egen- uses =fcn(arguments)].

When there's a Wiki, I'll write that in it.  :)

Jeremy

On 07/01/07, n j cox <[email protected]> wrote:
```
```There is no need for guessing on this. If you
syntax of -egen- is

egen [type] newvar = fcn(arguments) [if] [in] [, options]

and so there is no scope for anything on the right-hand
side other than -if- or -in- stuff or options.

There is really is a world of difference between functions
(strict sense) and -egen- functions: in several ways use
of the same term is unfortunate, although a different
term would also not have been desirable.

In many contexts functions can be combined pretty well
arbitrarily with all kinds of other stuff in complicated
expressions, but with -egen- functions there is no
hidden flexibility -- except, as Scott Merrymsn indicated,
the flexibility you provide yourself as programmer
through options. Otherwise what you want requires two
lines.

Nick
[email protected]

Sergio Correia

I don't think you can't do it in one line. Even if you could, I think
that it would be a bad idea for more advanced uses of -egen-. Imagine
trying to understand (or even program!) something like:

egen x = 2+5*log(seq(), from(1) to(10) by(region))

On the other hand, with -generate- you can mix all the functions you
want, like in:
generate x = 3 * (price + mpg) / 2

Which is similar to what you did, except for the treatment of missing
values.

Jeremy Miles

Am I missing something obvious here, when I try to combine two steps
into one line:
. sysuse auto
. egen x = rowmean(price mpg) * 3

Stata says:
varlist not allowed
r(101);

For:
. egen x = 3 * rowmean(price mpg)

Stata says:
r(198);
(Invalid syntax)

I can do it in two steps, but that seems inelegant.  Have I missed
something obvious?

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```
```
--

Jeremy Miles
www.jeremymiles.co.uk
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```