Lazy evaluation in '. R.' refers to the delayed execution of code until the result is actually needed. This means that expressions are not evaluated immediately, but rather when their value is explicitly requested. This concept is advantageous in scenarios where you have large datasets or complex calculations, as it allows you to save memory and improve performance by only computing what is necessary. Additionally, lazy evaluation can help optimize code by enabling the use of control flow functions like 'ifelse()' and 'switch()' efficiently.

Lazy evaluation is a powerful feature in '. R.' that enables more efficient and effective programming. It allows us to avoid unnecessary computations and only evaluate expressions as needed. This can be especially beneficial when dealing with iterative algorithms or when working with large datasets. By deferring evaluation until necessary, lazy evaluation helps optimize memory usage and improves overall performance.