The with() function applies an expression to a dataset, and the by() function applies a function to each level of factors.

The lapply is used to show the output in the form of the list, whereas sapply is used to show the output in the form of a vector or data frame.

The statement is not entirely accurate. The with() function in R is used to evaluate an expression in an environment created by a data frame. It can be useful for simplifying code by allowing you to refer to variables in the data frame directly, without using the $ operator.

On the other hand, the by() function is used for applying a function to subsets of a data frame, split by one or more factors. It is often used in conjunction with the tapply() function.

So, the correct answer would be:

“The with() function applies an expression to a dataset by creating an environment, allowing direct access to variables. In contrast, the by() function applies a function to each level of factors in a data frame, allowing for the computation of summary statistics or other operations on subsets of the data.”