Vectorized Operations

Primary source: Art of R Programming, Matloff

Data Frames can be thought of as collections of vectors
? - What is the difference between a data frame and a matrix?

• Key dataframe concepts

• vectorization: where functions are applied element-wise to vectors
• recycling

• filtering

x = rep(8,6)
x    # valuable license plate in Hong Kong
str(x)

u <- c(5, 2, 8)
v <- c(1, 3, 9)

u > v

w <- function (x) return (x + 1)

w(u)

# + operator is vectorized; really is a function!
'+'(2,3)

y <- c(1.2, 3.9, 0.2)
round(y)

u == v
identical(u, v)

When we discuss factors, we’ll look at ifelse() and tapply():

• ifelse() - vectorized if-else-then
• apply() - apply family – functions across groups of objects