Checking if string is in uppercase in R

regex r uppercase
topchef picture topchef · Feb 24, 2014 · Viewed 16.6k times · Source

Is there simpler method to match regex pattern in its entirety? For example, to check if given string is uppercase the following 2 methods but seem too complex. Checking stringr I found no indication for simpler solution either.

Method 1:

isUpperMethod1 <- function(s) {
  return (all(grepl("[[:upper:]]", strsplit(s, "")[[1]])))
}

Method 2:

isUpperMethod2 <- function(s) {
  m = regexpr("[[:upper:]]+", s)
  return (regmatches(s, m) == s)
}

I intentionally omit handling of empty, NA, NULL strings to avoid bloated code.

The uppercase pattern can be generalized to arbitrarily regex pattern (or character set).

I see no problems with both solutions above except that they seem excessively complex for the problem solved.

Answer

Matthew Plourde picture Matthew Plourde · Feb 24, 2014

You can use the ^ and $ patterns to match the beginning and end of the string

grepl("^[[:upper:]]+$", s)

Related questions

Replace specific characters within strings

I would like to remove specific characters from strings within a vector, similar to the Find and Replace feature in Excel. Here are the data I start with: group <- data.frame(c("12357e", "12575e", "197e18", "e18947") I start …

Read More
Test if characters are in a string

I'm trying to determine if a string is a subset of another string. For example: chars <- "test" value <- "es" I want to return TRUE if "value" appears as part of the string "chars". In the following …

Read More
Selecting data frame rows based on partial string match in a column

I want to select rows from a data frame based on partial match of a string in a column, e.g. column 'x' contains the string "hsa". Using sqldf - if it had a like syntax - I would do …

Read More