startsWith

Determine if strings start with pattern

Syntax

TF = startsWith(str,pattern)

TF = startsWith(str,pattern,'IgnoreCase',true)

Description

TF = startsWith(str,pattern) returns 1 (true) if str starts with the specified pattern, and returns 0 (false) otherwise.

If pattern is an array containing multiple patterns, then startsWith returns 1 if it finds that str starts with any element of pattern.

TF = startsWith(str,pattern,'IgnoreCase',true) ignores case when determining if str starts with pattern.

Examples

Determine If String Starts with Pattern

Create a string array that contains file names. Determine which file names start with the word data.

Starting in R2017a, you can create strings using double quotes.

str = ["abstract.docx","data.tar","code.m"; ...
       "data-analysis.ppt","results.ptx","summary.ppt"]

str = 2x3 string
    "abstract.docx"        "data.tar"       "code.m"     
    "data-analysis.ppt"    "results.ptx"    "summary.ppt"

Return a logical array where the position of each element equal to 1 corresponds to the position of a string in str that starts with data.

pattern = "data";
TF = startsWith(str,pattern)

TF = 2x3 logical array

   0   1   0
   1   0   0

Display the file names that start with data. Index back into str using TF.

str(TF)

ans = 2x1 string
    "data-analysis.ppt"
    "data.tar"

Test Start of String Against Multiple Patterns

Create a string array that contains file names. Determine which file names start with either abstract or data.

Starting in R2017a, you can create strings using double quotes.

str = ["abstract.docx","data.tar.gz","mycode.m","results.ptx"]

str = 1x4 string
    "abstract.docx"    "data.tar.gz"    "mycode.m"    "results.ptx"

pattern = ["abstract","data"];
TF = startsWith(str,pattern)

TF = 1x4 logical array

   1   1   0   0

Display the strings that start with either abstract or data. Index back into str using TF.

str(TF)

ans = 1x2 string
    "abstract.docx"    "data.tar.gz"

Ignore Case When Testing Start of String

Create a string array that contains file names. Determine which file names start with data, ignoring case.

Starting in R2017a, you can create strings using double quotes.

str = ["DATA.TAR.GZ","data.xlsx","SUMMARY.PPT","tmp.gz"]

str = 1x4 string
    "DATA.TAR.GZ"    "data.xlsx"    "SUMMARY.PPT"    "tmp.gz"

pattern = "data";
TF = startsWith(str,pattern,'IgnoreCase',true)

TF = 1x4 logical array

   1   1   0   0

Display the strings that start with data. Index back into str using TF.

str(TF)

ans = 1x2 string
    "DATA.TAR.GZ"    "data.xlsx"

Determine if Character Vector Starts with Pattern

Create a character vector that contains the name of a file. Determine if the name starts with different patterns.

chr = 'data-analysis.ppt'

chr = 
'data-analysis.ppt'

TF = startsWith(chr,'data')

TF = logical
   1

TF = startsWith(chr,'test')

TF = logical
   0

Input Arguments

str — Input text

string array | character vector | cell array of character vectors

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

pattern — Search pattern

string array | character vector | cell array of character vectors

Search pattern, specified as a string array, a character vector, or a cell array of character vectors.

Extended Capabilities

Tall Arrays

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

This function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• str and pattern must be a string scalar, a character vector, or a cell array containing not more than one character vector.

Distributed Arrays

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

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