Problem:
Pattern Matching and Replacement of an occurrence of a Substring in R with some other Substring.
Solution:
The Replacement Functions in R are as below:
- sub(): Replaces the first occurrence of a pattern
- gsub(): Replaces all occurrence of a pattern
The syntax for the sub() and the gsub() Functions:
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sub(pattern, replacement, x, ignore.case )
gsub(pattern, replacement,x, ignore.case)
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pattern – A Regular Expression to search for i.e. the old substring that needs to be replaced – A new substring to replace the occurrence (or occurrences for gsub) of the pattern.
Syntax Of Regular Expressions:
The position of pattern within the string:
-
^: matches the start of the string.
-
$: matches the end of the string.
-
b: matches the empty string at either edge of a word. Don’t confuse it with ^ $ which marks the edge of a string.
-
B: matches the empty string provided it is not at an edge of a word.
-
*: matches at least 0 times.
-
+: matches at least 1 times.
-
?: matches at most 1 times.
-
{n}: matches exactly n times.
-
{n,}: matches at least n times.
-
{n,m}: matches between n and m times.
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| Sub() Output |
sub() function has replaced only the first occurrence of the term “Datalogy”.
gsub() function has replaced both the occurrence of the term “Datalogy” and even the case is ignored.
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| gsub() Output |