Re: st: handling missing values

["Michael I. Lichter" <mlichter@buffalo.edu>]

Jillian,

If I understand you correctly, what you want is the following. Supposing 
that 1 = yes, 2 = no, 7 = dk, and 9 = ref (or something along those lines):

clonevar q2r = q2
replace q2r = q1 if ((q2r == .) & (q1 > 1)).

The parentheses are optional, and the clonevar is to keep you from 
clobbering your original q2 variable. Be sure to check first for cases 
where q1==no & q2==yes, etc., which might indicate data entry errors or 
problems with people not following skip patterns properly.

You would do virtually the same thing in SPSS; SPSS gives you no 
particular advantage in this instance.

What SPSS has that every other language lacks (to my knowledge) is the 
ability to assign specific values or ranges to missing without changing 
the content of the underlying variable. That is, you can tell SPSS that 
"9" is missing, and SPSS will treat every "9" in the variable as missing 
without you having to change all of the 9s to "." SPSS, however, cannot 
treat missing values on one variable differently conditional on values 
of a second variable.

Michael

Jillian Flight wrote:
> Hi there,
> I am working on a survey data recode and wanted to see if there is an easy
> way to handle missing values.   For instance, if question 1 asks whether or
> not respondent used cocaine in lifetime - and the responses are yes, no,
> don't know and refused.  Question 2 (have you used in past 12 months -
> response choices yes, no, dk, ref )  however is asked only of those who
> said yes to question 1 - the no, dk, and refused responses from Question 1
> are missing - - is there a quick and easy way to recode question 2 so that
> it is among the total population - ie. the missing values that are a result
> of respondents saying "no" to question 1 being coded into the "no" of
> question 2 and the dk and refused choices from question 1 which are now
> missing in question 2 - having them coded into the dk and refused of
> question 2?  I am currently doing this via a very convaluded method and a
> colleague told me spss is much easier for handling missing values when
> recoding data such as this, but I'm thinking there must be an easy way of
> doing this in stata.
>
> Thanks
>
>
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--
Michael I. Lichter, Ph.D.
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 125 / Phone: 716-898-4751 / E-Mail: mlichter@buffalo.edu

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