Final answer:
The question involves nested list indexing in R, and the provided snippet contains a typo that would result in an error. Correctly indexing a nested list would require using the indexing vector appropriately. The student's request would cause an error since the first sublist does not have a third element.
Step-by-step explanation:
The question pertains to indexing elements within nested lists in the R programming language, specifically extracting elements using a complex indexing vector. Given an R list x defined as x <- list(a = list(10,12,14), b = c(3.14,2.81)), the query x[[c(1,3)]] attempts to extract the third element within the first sub-list of x.
However, there's an issue with the syntax, and the student's question contains a typo which would cause an error in R. If the list x was correctly constructed and assuming the typo is ignored, the correct extraction would look like x[[c(1,3)]], which means to take the first element of x, which is a sublist, and then from this sublist take the third element. Nonetheless, since the sublist only contains two elements (10, 12), this would result in an error because there is no third element to extract.
To perform nested indexing without error, assuming the sublist has enough elements, you export the element by using the indexing vector correctly according to the structure of the list. If the student intended to extract the first element of the first sub-list of x, the correct code would be x[[c(1, 1)]], which returns 10, the first element of the first sublist. If there was a third element and we want to extract that, we would use x[[c(1, 3)]], but in this scenario with the sublist list(10,12,14), that code would return 14.