Regular Expressions

Using text editors in conjunction with Excel.

• Good text editors (Text Wrangler, Notepad++) can transform line endings for you if you have trouble importing a saved document.
• Copy and paste to remove functions and keep values, if you are using a tab-delimited file.
• Some things are just easier to do in text editors.

What are regular expressions?

• Fancy search and replace using strings. Can be relatively simple if you know a few basic rules.

Exercises

1. Open the grid11.txt file in your text editor
2. Turn on invisibles.
3. Remove all empty lines (^\n)
4. Flip long and lat.

Basic matching

Wildcards: *.txt (finds any thing with a .txt ending)

\w = a word character [A-Za-z0-9_]

\t = a tab character

\s = a whitespace character that matches a space, a tab, a line break, or a form feed.

\S = a non-whitespace character.

\r \n = an end of line character.

\d = a digit from 0-9.

Anchors

^ = The match must start at the beginning of the string or line.

$ = The match must occur at the end of the string or before \n at the end of the line or string.

Quantifiers

{} = [\d{3}] Match any 3 decimal digits.

• = makes it greedy

. = any letter, number or symbiol except end of line characters. Same as saying "add one character".

Character Groups

[] = defines a character group

[^aeiou] = everything but what is in the character group

[answers: (^\S+)(.)(-\S+); $3$2$1 or \3\2\1]

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