RE: st: A bug in egen and gen?

[David Kantor <kantor.d@att.net>]

At 09:43 PM 2/17/2011, Junlin wrote:
> Unless someone changed the command, my version of Stata 11 does not 
> compress double to float when it can do so. This is also indicated 
> in the documentation. However, I can recast a variable to float if 
> there is no loss of precision, otherwise I have to put in the /force 
> option to force convert with loss of precision.

You may want to check
-ssc desc doubletofloat-

While -compress- does recast double to long, int or byte, it does not 
go double to float. Typing -recast float ...- is easy, but 
-doubletofloat- provides some additional convenience.

You may also be interested in
-ssc desc floattolong-
That does not save space, but recasts to a possibly more appropriate type.
I use long, int, or byte, (depending on the range) whenever the value 
are sure to be integer.
What I'd like to see is an 8-byte integer type. Could be useful in 
some circumstances, for several reasons.

Finally, in response to Nick's comment,...

> You always have to tell -generate-, etc. what variable type you
> want created. On the whole, I don't think that would be a popular
> change.

This is my choice. Maybe it's a result of my programming background, 
but when I create a variable, the first thing I want to know is what 
data type it should be. What kinds of values -- integer or 
fractional? What range? Based on that, I choose the appropriate type. 
A command such as,
gen a = ...
looks risky to me, and I rarely do it. (I would do it only in 
manually-typed experiments. I would never do that in "live" work.) It 
could possibly have different results in different circumstances 
(depending on the default type). This habit is so ingrained, that I 
sometimes write,
gen float a = ...

In summary, I almost never depend on the default; I work as if the 
data type were a required feature of -gen- and -egen-.
HTH
--David

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/