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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: multiple response to binary |

Date |
Fri, 12 Jul 2002 17:57:56 +0100 |

Lee Sieswerda > I have a data management problem (WinNT4, Stata v7). > > I have data from a questionnaire where some of the questions allow the > respondent to choose multiple responses. Lets say there 7 > possible responses > and they could choose any number of them. I would code this as a set of 7 > binary variables. Unfortunately, the way it was coded was not so > straightforward. It was coded across 7 variables, but the responses were > simply entered in the order in which they were given by the respondent. So > the data look like this: > > f4m1 f4m2 f4m3 f4m4 f4m5 f4m6 f4m7 > 1 7 4 . . . . > 1 . . . . . . > 1 . . . . . . > 1 . . . . . . > 7 3 . . . . . > 1 . . . . . . > 1 2 3 4 . . . > 1 2 3 4 6 . . > 1 2 7 . . . . > 1 . . . . . . > > As you can see, you cannot simply tabulate the number of people who > responded 1, 2 , 3 etc because the responses are scattered over the 7 > variables in a different order for every person. The folks who provided me > with this data use SPSS and they get around this problem by using > "multiple > responses sets". In SPSS, you can define a set of variables as a multiple > response set (in this case, seven variables) and then ask for tables of > frequencies and crosstabs generated from across the 7 variables. It works, > but I'd much rather use Stata than SPSS. Also, the SPSS solution > is limited > to simple tables and doesn't permit you to get chi-square or other > statistics. > > Now, in Stata I know I can generate dummy variables from this mess like > this: > gen dum1 = 0 > replace dum1 = 1 if f4m1==1 | f4m2==1 | f4m3==1 etc. > replace dum1 = . if f4m1==. & f4m2==. & f4m3==. etc. > gen dum2 = 0 > etc. > > However, this is tedious in the extreme and there are many of > these multiple > response questions in the dataset. I could automate the procedure somewhat > using -foreach-, but its still more brute force than elegance. > Someone told > me about a SAS solution to this problem using an array procedure. Does > anyone have a nice elegant Stata solution to this problem? Is this what you want? 1. Use -tabm- from -tab_chi- on SSC. Advantage: You keep the same data structure. Disadvantage: Ugly table. . l f4m1 f4m2 f4m3 f4m4 f4m5 f4m6 f4m7 1. 1 7 4 . . . . 2. 1 . . . . . . 3. 1 . . . . . . 4. 1 . . . . . . 5. 7 3 . . . . . 6. 1 . . . . . . 7. 1 2 3 4 . . . 8. 1 2 3 4 6 . . 9. 1 2 7 . . . . 10. 1 . . . . . . . tabm f4m? | Values Variable | 1 2 3 4 6 | Total -----------+-------------------------------------------------------+-------- -- f4m1 | 9 0 0 0 0 | 10 f4m2 | 0 3 1 0 0 | 5 f4m3 | 0 0 2 1 0 | 4 f4m4 | 0 0 0 2 0 | 2 f4m5 | 0 0 0 0 1 | 1 -----------+-------------------------------------------------------+-------- -- Total | 9 3 3 3 1 | 22 | Values Variable | 7 | Total -----------+-----------+---------- f4m1 | 1 | 10 f4m2 | 1 | 5 f4m3 | 1 | 4 f4m4 | 0 | 2 f4m5 | 0 | 1 -----------+-----------+---------- Total | 3 | 22 . tabm f4m? , trans | Variable Values | f4m1 f4m2 f4m3 f4m4 f4m5 | Total -----------+-------------------------------------------------------+-------- -- 1 | 9 0 0 0 0 | 9 2 | 0 3 0 0 0 | 3 3 | 0 1 2 0 0 | 3 4 | 0 0 1 2 0 | 3 6 | 0 0 0 0 1 | 1 7 | 1 1 1 0 0 | 3 -----------+-------------------------------------------------------+-------- -- Total | 10 5 4 2 1 | 22 Or 2. You -reshape- to long. Advantage: Much nicer tables, more control. Disadvantage: Different data structure. . gen id = _n . reshape long f4m , i(id) . table f4m _j ---------------------------------------- | _j f4m | 1 2 3 4 5 ----------+----------------------------- 1 | 9 2 | 3 3 | 1 2 4 | 1 2 6 | 1 7 | 1 1 1 ---------------------------------------- . table _j f4m ---------------------------------------------- | f4m _j | 1 2 3 4 6 7 ----------+----------------------------------- 1 | 9 1 2 | 3 1 1 3 | 2 1 1 4 | 2 5 | 1 ---------------------------------------------- Nick n.j.cox@durham.ac.uk * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: multiple response to binary***From:*Lee Sieswerda <Lee.Sieswerda@tbdhu.com>

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