Assignment, Types and Basic Operations

The building blocks

Assign values with <- (the conventional R assignment operator; = also works at the top level, and RStudio inserts <- with Alt and minus). Names are case-sensitive and conventionally use snake_case. R's basic atomic types are double (numbers, the default: 3 is a double), integer (written with L: 3L), character (strings in double or single quotes), logical (TRUE/FALSE), complex and raw. Even a single value is a vector of length one. Check types with typeof(), class() and functions such as is.numeric(), and convert with as.numeric(), as.character() and as.integer() (failed conversions produce NA with a warning). Special values: NA (missing value, which propagates: NA + 1 is NA), NULL (absence of a value), NaN (not a number) and Inf. Arithmetic includes %/% (integer division) and %% (remainder). Use paste()/paste0() or sprintf() to build strings, and print(), cat() or simply typing a name in the console to see values.

Types, conversions and missing values

NA propagates through calculations unless you remove it explicitly.

price <- 499.5                 # double
qty <- 3L                      # integer
city <- "Pune"                 # character
in_stock <- TRUE               # logical

typeof(qty)                    # "integer"
class(price)                   # "numeric"

total <- price * qty
paste0("Total for ", qty, " items in ", city, ": ", total)
sprintf("%.2f INR", total)

as.numeric("42")               # 42
as.numeric("forty-two")        # NA with a warning

marks <- c(72, NA, 90)
mean(marks)                    # NA: missing values propagate
mean(marks, na.rm = TRUE)      # 81: ignore missing values

17 %/% 5                       # 3 (integer division)
17 %% 5                        # 2 (remainder)

NA is contagious

Any calculation involving NA returns NA, and x == NA is always NA, never TRUE. Use is.na(x) to test for missing values and na.rm = TRUE in summary functions.

त्वरित जाँच: What does mean(c(72, NA, 90)) return?

• 81
• 0
• NA
• An error