Lecture 5

R Basics; Descriptive Statistics

Byeong-Hak Choe
bchoe@geneseo.edu

SUNY Geneseo

September 10, 2024

R Basics

Workflow: Quotation marks, parentheses, and +

x <- "hello
  • Quotation marks and parentheses must always come in a pair.
    • If not, Console Pane will show you the continuation character +:
  • The + tells you that R is waiting for more input; it doesn’t think you’re done yet.

R Basics

Functions

  • A function can take any number and type of input parameters and return any number and type of output results.

  • R ships a vast number of built-in functions.

  • R also allows a user to define a new function.

  • We will mostly use built-in functions.

R Basics

Functions, Arguments, and Parameters

library(tidyverse)

# The function `str_c()`, provided by `tidyverse`, concatenates characters.
str_c("Data", "Analytics")
str_c("Data", "Analytics", sep = "!")

  • We invoke a function by entering its name and a pair of opening and closing parentheses.

  • Much as a cooking recipe can accept ingredients, a function invocation can accept inputs called arguments.

  • We pass arguments sequentially inside the parentheses (, separated by commas).

  • A parameter is a name given to an expected function argument.

  • A default argument is a fallback value that R passes to a parameter if the function invocation does not explicitly provide one.

R Basics

Arithmetic Operations and Mathematical Functions

5 + 3
5 - 3
5 * 3
5 / 3
5^3
( 3 + 4 )^2
3 + 4^2
3 + 2 * 4^2
3 + 2 * 4 + 2
(3 + 2) * (4 + 2)

  • All of the basic operators with parentheses we see in mathematics are available to use.

  • R can be used for a wide range of mathematical calculations.

5 * abs(-3)
sqrt(17) / 2
exp(3)
log(3)
log(exp(3))
exp(log(3))
  • R has many built-in mathematical functions that facilitate calculations and data analysis.
  • abs(x): the absolute value \(|x|\)
  • sqrt(x): the square root \(\sqrt{x}\)
  • exp(x): the exponential value \(e^x\), where \(e = 2.718...\)
  • log(x): the natural logarithm \(\log_{e}(x)\), or simply \(\log(x)\)

R Basics

Vectorized Operations

a <- c(1, 2, 3, 4, 5)
b <- c(5, 4, 3, 2, 1)

a + b
a - b
a * b
a / b
sqrt(a)
  • Vectorized operations mean applying a function to every element of a vector without explicitly writing a loop.
    • This is possible because most functions in R are vectorized, meaning they are designed to operate on vectors element-wise.
    • Vectorized operations are a powerful feature of R, enabling efficient and concise code for data analysis and manipulation.