Grep(x = data_pkgs, pattern = "data.r", value = TRUE, ignore.case = TRUE) # "data.world" "datadogr" "dataRetrieval" Grep(x = data_pkgs, pattern = "data.r", value = TRUE, ignore.case = TRUE) # "datadr" "dataframes2xls" "dataPreparation" # package name includes the string data followed by any 3 characters and then the letter r # "archdata" "assertive.data" # package name includes the string data followed by any character and then the letter r Head(data_pkgs) # "abc.data" "acss.data" "adeptdata" "adklakedata" # extract package names that include the string dataĭata_pkgs <- grep(x = r_packages, pattern = "data", value = TRUE) To match more than 1 character, you need to specify as many dots. Keep in mind that it will match only 1 character and if you want (dot) is a wildcard character as it will match any character except a Special characters mentioned in the table but ensure that you use a different # "aws.sqs" "aws.transcribe" "aws.translate" # "aws.alexa" "aws.cloudtrail" "aws.comprehend" # "assertive.strings" "assertive.types" "auto.pca" # "assertive.properties" "assertive.reflection" "ts" # "assertive.matrices" "assertive.models" "assertive.numbers"
# "" "assertive.datetimes" "assertive.files" # "aroma.affymetrix" "aroma.apd" "aroma.cn" # "ANOVA.TFNs" "ar.matrix" "archivist.github" grep(x = r_packages, pattern = "\\.", value = TRUE) # "abc.data" "ABC.RAP" "acss.data" Match any character other than \n (new line). It is also known as wildcard character i.e. it is used to Why is this happening? A dot is special character in If you look at the output, it includes names of even those package names whichĪre not separated by dot. # "accelmissing" "AcceptanceSampling" "ACCLMA" grep(x = r_packages, pattern = ".", value = TRUE) # "A3" "abbyyR" "abc" In the firstĮxample, we want to detect package names separated by a dot. Now that we know the meta characters, let us look at some examples. The below table displays the metacharacters: Meta characters are a special set of characters not captured by regularĮxpressions i.e. if these special characters are present in a string, regularĮxpressions will not detect them.
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