7.8: Checking Text Types and Properties

Sometimes a program needs to check what kind of text it has, or what kinds of characters appear inside the text. The functions isstring, ischar, and isStringScalar are used for this purpose.

Function	Returns true when...
isstring(x)	x is a string array.
isStringScalar(x)	x is a single string scalar.
ischar(x)	x is a character vector or character array.

Exercise \(\PageIndex{1}\)

Run the following commands and pay close attention to what MATLAB returns.

sampleStr = "Hello World";

sampleArr = 'Hello World';



result_1 = isstring(sampleStr)

result_2 =isstring(sampleArr)

result_3 =ischar(sampleStr)

result_4 = ischar(sampleArr)

Checking Individual Character Properties

The function isstrprop checks each character in a character vector and reports whether that character belongs to a category such as alphabetic, digit, lowercase, uppercase, or whitespace.

Exercise \(\PageIndex{2}\)

Run the following commands and pay attention to the results.


arr = 'eKtM 123';

result_1 = isstrprop(arr, 'alpha')

result_2 = isstrprop(arr, 'alphanum')

result_3 = isstrprop(arr, 'lower')

result_4 = isstrprop(arr, 'digit')

result_5 = isstrprop(arr, 'wspace')

The result is a logical array. Each position in the result corresponds to one character in the original text. A 1 means true, and a 0 means false.

The following table lists the isstrprop categories and their meaning.

Category	Meaning
'alpha'	Alphabetic letters.
'alphanum'	Letters or digits.
'digit'	Numeric digits such as 0, 1, 2, ..., 9.
'lower'	Lowercase letters.
'upper'	Uppercase letters.
'wspace'	Whitespace, such as spaces, tabs, and newline characters.

Here are a few other property functions and what they do:

Function	What it does
isletter	Checks for alphabetic letters.
isspace	Check for whitespace characters
iskeyword	Checks whether the input is a reserved MATLAB keyword, such as for, if, or end.

Exercise \(\PageIndex{3}\)

Run the following commands and pay attention to the results.


arr = 'ek 123 ';

result_1 = isletter(arr)

result_2 = isspace(arr)

result_3 = iskeyword(arr)

result_4 = iskeyword('for')