Partial matching of names is allowed with ___, for example: A) x<- list(aardvark = 1:5) B) x$a gives back ___ C) x[[""a""]] gives back___ D) x[["&quo…

Question

Partial matching of names is allowed with ___, for example:

A) x<- list(aardvark = 1:5)
B) x$a gives back ___
C) x[[""a""]] gives back___
D) x[[""a"", exact = FALSE]]

Answer 1

This is about using the R programming language to perform partial matching of list element names. Using x$a or x[["a", exact = FALSE]] retrieves elements in list x by partial name matching, where 'a' partially matches 'aardvark'. Exact matching, x[["a"]], generally returns an error unless exact = FALSE is specified.

Step-by-step explanation:

The question pertains to the R programming language, and more specifically, to partial matching of list elements by their names using the extraction operator. When you create a list in R with named elements, you can retrieve the elements not only by using the exact names but also by partial matching if the name is unique enough to be distinguishable.

Given the example list x:

x <- list(aardvark = 1:5)

Here are the answers to the sub-questions:

• B) Using x$a will return the values associated with 'aardvark', as 'a' is a unique partial match in list x.
• C) x[["a"]] will typically result in an error, as exact matching is required by default when using double brackets.
• D) x[["a", exact = FALSE]] allows for non-exact matching and will return the values associated with 'aardvark', just as x$a does.

Note that partial matching can be risky if multiple elements in the list start with the same initial character(s); it's generally safer to use exact names to avoid ambiguity.