Week 11.pdf - Week 11 Tuesday 1:28 AM Object-oriented...

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R's classes support object-oriented programming can write one func for ALL objects Allows manipulation of objs w/o knowing their type Can change how obj works w/o changing all functions that use it Permit the kinds of things done to objects ("methods") and to what kind of objects ("classes") w/o changing existing funcs Object-oriented programming > a <- as.factor(c("red","green","yellow","red","green","blue","red")) > a [1] red green yellow red green blue red Levels: blue green red yellow > class(a) # We can see that this object has the class "factor" [1] "factor" > unclass(a) # Here’s what it is without its class attribute [1] 3 2 4 3 2 1 3 attr(,"levels") [1] "blue" "green" "red" "yellow" Represents a vector of strings as vector of integers + vector of distinct string values Strings are converted to factors in read.table, unless you use the stringsAsFactors=FALSE option Here, integers = levels No mathematical operations can be performed, despite being integers Factor class > x <- 9 > class(x) <- "mod17" > x + 10 [1] 19 attr(,"class") [1] "mod17"
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