# Indexing

Want to learn more? I recommend working through: R for Data Science, R Cookbook, and R Graphics Cookbook.

** How indexing is formatted:**

`variable[ row(s), column(s) ]`

# Create a variables of five elements x <- c(1, 4, 9, 16, 25) y <- c(1, 4, 4, 36, 24) m <- data.frame(x, y)

# Select the first, third, and fifth elements x[c(1,3,5)]

[1] 1 9 25

# Select of all EXCEPT the second and fourth elements x[c(-2, -4)]

[1] 1 9 25

# Select of all EXCEPT the second and fourth elements x[c(TRUE, FALSE, TRUE, FALSE, TRUE)]

[1] 1 9 25

# Select the entire first row of a matrix, array, or dataframe m[1, ]

x y 1 1 1

# Select an the entire first column of a matrix, array, or dataframe m[, 1]

[1] 1 4 9 16 25