Vectors

• sequence of values with the same type
• make one using c(): sites <- c("a", "a", "b", "b")
• explore: str(sites), length(sites)
• Use the Tab key for autocomplete: Let the computer do repetitious work, easier, few mistakes
• slicing: sites[1], sites[1:3], 1:3 makes a vector so this is the same as sites[c(1, 2, 3)] which you can use to get any subset or order you want
• math:

counts <- c(0, 2, 2, 6)
weights <- c(1.5, 2.6, 8.4, 0.2)
sum(counts)
max(weights)
total_weight <- sum(weights)

• subsetting: counts[sites == 'a']
• == means “equal to” in most languages; = means assignment

Exercise 1

Matrices (if linear algebra folks)

x <- matrix(1:6, 2)
y <- matrix(1:3, ncol = 1)
x %*% y

Data Frames

• A list of equal length vectors grouped together
• Create: surveys <- data.frame(sites, counts, weights) or read.csv
• Explore: str(surveys), length(surveys), nrow(surveys),ncol(surveys)
• Subsetting columns

surveys["sites"]
surveys[c("counts", "weights")]
surveys$sites
surveys[["sites"]]

• Subsetting rows: subset(surveys, sites == 'a')
• Subsetting values/blocks: surveys[1,2], surveys[1:2,1:3]

Exercise 3