R – detecting word boundary with regex in data frame in R

dataframerregexword-boundary

I have a data.frame named all that has a column of factors, these factors include "word","nonword" and some others. My goal is to select only the rows that have the factor value "word".

My solution grep("\bword\b",all[,5]) returns nothing.

How come word boundaries are not recognized?

Best Answer

In R, you need two times \:

grep("\\bword\\b", all[5])

Alternative solutions:

grep("^word$", all[5])

which(all[5] == "word")

Related Solutions

R – Drop unused factor levels in a subsetted data frame

Since R version 2.12, there's a droplevels() function.

levels(droplevels(subdf$letters))

Regex – a word boundary in regex

A word boundary, in most regex dialects, is a position between \w and \W (non-word char), or at the beginning or end of a string if it begins or ends (respectively) with a word character ([0-9A-Za-z_]).

So, in the string "-12", it would match before the 1 or after the 2. The dash is not a word character.

Best Answer

Related Solutions

R – Drop unused factor levels in a subsetted data frame

Regex – a word boundary in regex

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