[EpiData-list] Outbreak analysis with Epidata Analysis diary - 1 Data issues - text to Boolean

epidata-list at lists.umanitoba.ca epidata-list at lists.umanitoba.ca
Wed Jun 4 00:44:59 CDT 2008

We have an outbreak to deal with. Up to several hundred people are possiblly sick after attending a local sports venue that also hosts children's birthday parties. Like many outbreaks it comes at a difficult time (they seem to love happening on Christmas Eve or the day before Easter). This one we learn about the day before a holiday weekend and I have the day off the next day. 

Someone has designed a questionnaire asking our usual questions (Demographics, symptoms and exposures) and the phone calls have already started. I help someone create an Epidata questionnaire to enter the data and promise to help with the analysis on my return.

There are two main things we have to do in our outbreak analysis 
1. Describe the pattern of illness by person place and time  (how many people are sick with what symptoms, when did they get sick and for how long)
2. Discover if certain 'exposures' - e.g. eating certain foods are associated with illness.

Today I come back and find I have a problem I must fix before we start the analysis. My workmate has changed my file so all the Boolean fields I used to record the exposure information are now text fields. (She did this because she wanted to be able to put "U" for unknown. I explain we need the data in Boolean fields for our two by table analysis and if the answer is unknown to leave the field blank. She has entered 66 records already so I have a problem - how do I change the data from text to Boolean as changing a field type in Epidata from text to Boolean would lose all the data?

The way I work out is: (using the example outbreak.rec for the file that has data entered as text)

1. Use Save as with outbreak.qes to make a new file called outbreak2.qes. Change this file so the txt fields are now boolean fields
2. Create a new blank rec file from outbreak2.qes called outbreak2.rec
3. Export outbreak.rec to Excel as outbreak2.xls
4. Use search and replace to change the Y,  N and U  that have been entered to 1,0 and blank
5. Save Outbreak.xls  to a text file outbreak2.csv (CSV)
6. Import outbreak2.csv as a text file ticking the option to not use first line. This 'pulls' the data into outbreak2.rec and the boolean fields with the 1 and 0 showing as Yes and No
This seems a long way round so maybe someone has a better way to fix this problem? Next posting I will start with the analysis 



Christine Roseveare
Regional Public Health
570 9194
027 495 9671

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