Dataframes: What's a data frame?

You may remember the matrix, a multi-dimensional object that we discussed earlier. All the elements that you put in a matrix should be of the same type. However, when performing a market research survey, you often have questions such as:

• 'Are your married?' or 'yes/no' questions (= boolean data type)
• 'How old are you?' (= numeric data type)
• 'What is your opinion on this product?' or other 'open-ended' questions (= character data type)

The output, namely the respondents' answers to the questions formulated above, is a data set of different data types. You will often find yourself working with data sets that contain different data types instead of only one. A data frame has the variables of a data set as columns and the observations as rows. This will be a familiar concept for those coming from different statistical software packages such as SAS or SPSS.