R objects that reside in other R objects can require a lot of typing to access. For example, to refer to a variable x in a dataframe df , one could type df$x . This is no problem when the dataframe and variable names are short, but can become burdensome when longer names or repeated references are required, or objects in complicated structures must be accessed.
Let's assume that we have a data frame x which contains the columns job and income . Referring to the data in the frame normally requires the commands x$job for the data in the job column and x$income for the data in the income column.