Working with data frames

A useful convention that allows you to work with many different problems comfortably together in the same working directory is

• gather together all variables for any well defined and separate problem in a data frame under a suitably informative name;

• when working with a problem attach the appropriate data frame at position 2, and use the working directory at level 1 for operational quantities and temporary variables;

• before leaving a problem, add any variables you wish to keep for future reference to the data frame using the $ form of assignment, and then detach();

• finally remove all unwanted variables from the working directory and keep it a clean of left-over temporary variables as possible.

In this way it is quite simple to work with many problems in the same directory, all of which have variables named x, y and z, for example.