Using R and RStudio for Data Management, Statistical Analysis, and Graphics, 2nd Edition

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“K23166” — 2015/1/28 — 9:35 — page 16 — #42

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16 CHAPTER 2. DATA MANAGEMENT

2.2.11 Set operations

newengland = c("MA", "CT", "RI", "VT", "ME", "NH")

"NY" %in% newengland

"MA" %in% newengland

Note: The first statement would return FALSE, while the second one would return TRUE.

The %in% operator also works with numeric vectors (see help("%in%")). Vector functions

for set-like operations include union(), setdiff(), setequal(), intersect(), unique(),

duplicated(), and match().

2.2.12 Find strings within string variables

Example: 7.10.9

matches = grep("pat", stringx)

positions = regexpr("pat", stringx)

> x = c("abc", "def", "abcdef", "defabc")

> grep("abc", ...