5.4 Inspecting data.frame objects

We’ve seen how str() can be useful to check the content and the structure of a data.frame. Here is a non-exhaustive list of functions to get a sense of the content/structure of the data.

• Size:
  • dim() - returns a vector with the number of rows in the first element, and the number of columns as the second element (the dimensions of the object)
  • nrow() - returns the number of rows
  • ncol() - returns the number of columns
• Content:
  • head() - shows the first 6 rows
  • tail() - shows the last 6 rows
• Names:
  • names() - returns the column names (synonym of colnames() for data.frame objects)
    
  • rownames() - returns the row names
    
• Summary:
  • str() - structure of the object and information about the class, length and content of each column
    
  • summary() - summary statistics for each column

Note: most of these functions are “generic”, they can be used on other types of objects besides data.frame.