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Re: Missing values [was: RE: st: simple question]


From   Steven Dubnoff <sdubnoff@circlesys.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: Missing values [was: RE: st: simple question]
Date   Thu, 03 Jun 2004 12:46:46 -0700


The bigger problem (which is perhaps more of an issue with Stat/Transfer than it is with Stata) is that distinctions between types of MD codes get lost when converting from SPSS to Stata. I don't know whether this problem is unique to Stata or occurs with other types of conversions as well, but I would like to see software better address it, e.g. when there are multiple MD codes in SPSS assign them to .a, .b, etc. in Stata.

We considered doing this when we added support for extended (a-z) missing value codes in SAS and Stata. The problem is complicated by fact that SPSS user missing values have no inherent meaning. All that we can do is assign the first missing value for a variable to .a and the second to .b, and so on. Which numeric values get assigned to each extended missing value will depend on the order in which they were defined in SPSS, which may or may not be known to the user.

Nonetheless, this feature has been requested often enough that it will put in the next version as an extension to our missing value handling option (all,first,none). A fourth option "extended" will map values, in the order defined in SPSS to .a, .b and .c.

If any users have any ideas for handling this in a more elegant manner, please contact me off list.

Best,

Steve




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Steven Dubnoff sdubnoff@circlesys.com
Circle Systems We make your data instantly usable.
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