MATLAB - Strings and Characters

MATLAB - Modern String Manipulation

Working with text is a fundamental part of programming, from reading data files to creating user interfaces. Modern MATLAB provides a powerful and intuitive string array type that makes text manipulation easier and more efficient than ever before.

The Modern string vs. Legacy char

It’s crucial to understand the two ways MATLAB handles text:

• string (Double Quotes): This is the recommended modern approach. A string is a dedicated data type for text. String arrays can hold texts of different lengths without padding, and they come with a rich set of functions for manipulation. Use double quotes ("") to create strings.
• char array (Single Quotes): This is the legacy approach. A char array is an array of individual characters. A 1xN char array is a ‘character vector’. To store multiple texts, you must use a MxN array where all rows have the same length (requiring padding with spaces) or use a cell array. You will still encounter this in older code.

Creating and Combining Strings

Creating strings is simple. To combine them, you can use the plus (+) operator, which intuitively concatenates strings and even converts numbers to text automatically.

Essential String Functions

The string type has many built-in functions that are called using dot notation, making code highly readable. These replace older str* functions.

Task	Modern string Function	Legacy char Function
Find substring	contains(str, pattern)	strfind, contains
Replace substring	replace(str, old, new)	strrep
Split string	split(str, delimiter)	strsplit, strtok
Join string array	join(str_array, delimiter)	strjoin
Convert to lower/upper case	lower(str), upper(str)	lower, upper
Check if starts/ends with	startsWith(str, pat), endsWith(str, pat)	N/A (manual)
Get length	strlength(str)	length

Example: Parsing Log Data

Imagine you have log entries and you need to extract specific information. string functions make this task simple.

Working with Legacy Code

You will inevitably encounter older code that uses char arrays. It’s easy to convert between the two types.

Best Practices

• Use string for new code. Its benefits in flexibility, readability, and functionality are significant.
• Use the + operator for simple concatenation. It’s clean and handles type conversion automatically.
• Use join to combine elements of an array, and split to break them apart. They are more robust than manual looping.
• Leverage function-form for clarity. Instead of str.lower(), using lower(str) is often more consistent with other MATLAB functions and can improve readability.
• When performance is critical for very large text data, char arrays can sometimes be faster as they have less overhead. However, for most applications, the convenience of string arrays outweighs this.