Chapter 7
More About Defining Your Data
In This Chapter
Understanding the special properties of dates and times
Creating multiple response sets
Copying variable definitions from another file
Without a definition, a number serves no purpose. For example, the number 3 could have entirely different meanings. It could be a number of miles, or an answer to a multiple-choice question, or the number of jelly beans in your pocket.
The data type is more than just a tag — it determines how the value can be manipulated. For example, date arithmetic (the distance in time between two dates) would be a nightmare to do without help. You would have to take into account leap years, and you may even have to worry about whether a day is a business day. So, it isn’t enough to merely declare that something is a date, as we do in Chapter 4. You have to make sure that the date is in the proper date format. As soon as you do that, you can take advantage of special menus for manipulating dates.
Multiple-response variables — those “check all that apply” questions on surveys — are another kind of variable type that needs extra attention. Again, when you do it properly, you can use a special menu dedicated to ...
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