面试题与答案

Vectorization is the process of applying operations to entire vectors at once. It is important for efficiency and simplicity in R programming.

Example:

vector1 <- c(1, 2, 3)
vector2 <- c(4, 5, 6)
result <- vector1 + vector2

Lazy evaluation is a feature in R where expressions are not evaluated until their values are actually needed. It can improve performance by avoiding unnecessary computations.

Example:

lazy_function <- function() { print('Lazy function') }
# The function is not executed until called: lazy_function()

You can use functions like runif() for uniform distribution, rnorm() for normal distribution, and sample() for random sampling.

Example:

random_numbers <- runif(5)

The 'shiny' package is used to create interactive web applications directly from R. It allows users to interact with R-based visualizations through a web browser.

Example:

library(shiny)
shinyApp(ui, server)

'Rcpp' is a package in R that provides facilities for seamless integration of C++ code in R. It allows for improved performance in computationally intensive tasks.

Example:

#include 
// C++ code with Rcpp
// ...

'dtplyr' is an extension of the 'dplyr' package designed for large datasets. It uses the 'data.table' package to improve performance in data manipulation operations.

Example:

library(dtplyr)
large_data %>% filter(Age > 30) %>% summarise(mean(Salary))

Memoization is a technique to cache and reuse the results of expensive function calls. In R, it can be implemented using the 'memoise' package.

Example:

library(memoise)
my_function <- memoise(function(x) { # function body })

Closures in R allow functions to capture and store the environment in which they were created. This is useful for creating functions with embedded data or behavior.

Example:

closure_function <- function() {
  x <- 10
  function() { x + 1 }
}