29. Objects
n Just about everything named in R is an object
n An object is a container that
n knows its class (eg, I have numbers inside!).
n has contents (eg, Actual numbers).
30. Examples of objects
n data, which you use for analysis (various classes)
n functions, which perform analysis (function class)
n results, which come out of analysis (various
classes)
31. Classes of data values
inside data objects
n Numeric: Continuous variables
n Factor: Categorical variables
n Logical: TRUE/FALSE binary variables
n etc...
32. Class?
n An object’s class tells R how the object should be
handled.
n For example, summarizing data should work
differently for numbers and categories!
33. Data objects
n Vector (contains single class of data values)
n List (contains multiple classes of data values)
34. Data objects
n Vector (contains single class of data values)
n Array including Matrix
n List (contains multiple classes of data values)
n Data frame
35. Vector
n Smallest building block of data objects
n Single dimension
n Combination of values of same class
n vec1 <- c(2013, 2, 15, -10) # combine
n vec2 <- 1:16 # integers 1 to 16
36. Array
n Vector folded into a multidimensional structure
n 2-dimensional array is a matrix
n vec3 <- 1:16
n dim(vec3) <- c(4, 4) # 4 x 4 structure
n dim(vec3) <- c(2, 2, 4) # 2 x 2 x 4 structure
n arr1 <- array(1:60, dim = c(3,4,5))
37. List
n Combination of any values or objects
n Can contain objects of multiple classes
n eg, a list of two vectors, a matrix, three arrays
n list1 <- list(first = 1:17, second = matrix(letters, 13,2))
n list2 <- list(alpha = c(1,4,5,7), beta = c("h","s","p","h"))
38. Data frame
n Special case of a list
n List of same-length vectors vertically aligned
n df1 <- data.frame(list2)
n list3 <- list(small = letters, large = LETTERS,
number = 1:26)
n df2 <- data.frame(list3)