Machine Learning with R Cookbook（Second Edition）

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The sub and gsub functions allow using regular expression to substitute a string. The sub and gsub functions perform the replacement of the first and all the other matches, respectively:

> sub("e", "q", names(iris))
Output:
[1] "Sqpal.Length" "Sqpal.Width"  "Pqtal.Length" "Pqtal.Width"  "Spqcies"     
> gsub("e", "q", names(iris))
Output:
[1] "Sqpal.Lqngth" "Sqpal.Width"  "Pqtal.Lqngth" "Pqtal.Width"  "Spqciqs"