R dummies

But in many practical situations, you’ll have data that have many differentclasses — in other words, you’ll have a mixture of numeric and character data. Inthis case, you need to use either lists or data frames.If you imagine your data as a single spreadsheet, a data frame is probably agood choice. Remember that a data frame is simply a list of named vectors of thesame length, which is conceptually very similar to a spreadsheet with columns anda column heading for each. If you’re familiar with databases, you can think of adata frame as similar to a single table in a database. Data frames aretremendously useful and, in many cases, will be your first choice of objects forstoring your data.If your data consists of a collection of objects but you can’t represent that asan array or a data frame, then a list is your ideal choice. Because lists can containall kinds of other objects, including other lists or data frames, they’re tremendouslyflexible. Consequently, R has a wide variety of tools to process lists.Table 13-1 contains a summary of these choices.You may find that a data frame is a very suitable choice for most analysisand data-processing tasks. It’s a very convenient way of representing yourdata, and it’s similar to working with database tables. When you read datafrom a comma-separated value (CSV) file with the function read.csv() orread.table(), R puts the results in a data frame.Table 13-1 Useful Objects for Data Analysis