extract

Extract substrings from strings

Since R2020b

Syntax

newStr = extract(str,pat)

newStr = extract(str,pos)

Description

newStr = extract(str,pat) returns any substrings in str that match the pattern specified by pat.

If str is a string array or a cell array of character vectors, then the function extracts substrings from each element of str. If pat is an array, then the function matches against multiple patterns.

newStr = extract(str,pos) returns the character in str at the position specified by pos.

Examples

Extract ZIP Codes from Addresses

Create a string array that contains addresses. Each address ends with a US ZIP code.

str = ["73 Beacon St., Boston, MA, 02116";
       "1640 Riverside Dr., Hill Valley, CA, 92530";
       "138 Main St., Cambridge, MA, 02138"]

str = 3x1 string
    "73 Beacon St., Boston, MA, 02116"
    "1640 Riverside Dr., Hill Valley, CA, 92530"
    "138 Main St., Cambridge, MA, 02138"

Create a pattern that matches any sequence of digits.

pat = digitsPattern

pat = pattern
  Matching:

    digitsPattern

Use it to extract all sequences of digits from the addresses.

newStr = extract(str,pat)

newStr = 3x2 string
    "73"      "02116"
    "1640"    "92530"
    "138"     "02138"

The digitsPattern pattern matches street numbers, apartment numbers, and ZIP codes. To match only ZIP codes, create a pattern that matches a sequence of digits at the end of an address.

pat = digitsPattern + textBoundary

pat = pattern
  Matching:

    digitsPattern + textBoundary

Extract the ZIP codes.

newStr = extract(str,pat)

newStr = 3x1 string
    "02116"
    "92530"
    "02138"

For a list of functions that create pattern objects, see pattern.

Extract Character at Numeric Position

Create a string.

str = "All's well that ends well"

str = 
"All's well that ends well"

Extract the first character in the string.

extract(str,1)

ans = 
"A"

Extract the last character.

extract(str,strlength(str))

ans = 
"l"

Input Arguments

str — Input text

string array | character vector | cell array of character vectors

Input text, specified as a string array, character vector, or cell array of character vectors.

pat — Search pattern

string array | character vector | cell array of character vectors | pattern array

Search pattern, specified as one of the following:

• String array

• Character vector

• Cell array of character vectors

• pattern array

pos — Position

numeric array

Position, specified as a numeric array.

If str is a string array or cell array of character vectors, then pos can be a numeric scalar or numeric array of the same size as str.

Output Arguments

newStr — Output text

string array | cell array of character vectors

Output text, returned as a string array or cell array of character vectors.

If str is a string array, then newStr is also a string array. Otherwise, newStr is a cell array of character vectors.

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

The extract function supports tall arrays with the following usage notes and limitations:

• If pat is an array of pattern objects, the size of the first dimension of the array must be 1.

For more information, see Tall Arrays.

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™. (since R2024b)

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced in R2020b