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substr

version 1.0.0.0 (4.42 KB) by Fernando Freitas Alves
Return part of a string.

4 Downloads

Updated 07 Oct 2016

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SYNTAX
str = substr(s,i,j)
str = substr(s,i,j,length_or_index)
DESCRIPTION
str = substr(s,i,j) returns the extracted part of s with length j beggining from i; or an empty vector if j < i or .
str = substr(s,i,j,length_or_index) the argument j is treated as the index of the last position of the substring inside s if length_or_index is equal to 'index'.

EXAMPLES

Outputs the substring from the second index position with a length of 3 chars.

str = substr('12345',2,3)
str =
'234'

Outputs the substring from the second to the third index position.

str = substr('12345',2,3,'index')
str =
'23'

INPUT ARGUMENTS

s — Input string
character vector or string scalar
String to extract a substring.
Data Types: string

i — Initial index
positive integer number
Number of the initial index inside str.
Data Types: double | single | int64 | int32 | int16 | int8

j — Length / End index
positive real number
Length of the output string if i > 0 or number of the end index inside str if length_or_index == 'index'.
Data Types: double | single | int64 | int32 | int16 | int8

length_or_index — Length or index
'length' (default) | 'index'
A string that interprets the input j as length when it is equal to 'length'.
or as an index when it is equal to 'index'.
Data Types: string

OUTPUT ARGUMENT

str — Substring
character vector or string scalar
String inside s.

Cite As

Fernando Freitas Alves (2021). substr (https://www.mathworks.com/matlabcentral/fileexchange/59560-substr), MATLAB Central File Exchange. Retrieved .

Comments and Ratings (1)

Stephen Cobeldick

Slow and unnecessary.

Rather than downloading this third-party function, all you need it to use basic MATLAB indexing. Using MATLAB indexing is simpler, faster, neater, easier to debug, is standard practice, and does not rely on any third-party functions. It is this simple:

>> str = '1':'5';
>> str(2:5)
ans = 2345
>> str(2:3)
ans = 23

Note that calculating those numeric indices will be much faster than this submission. Why? Because this function is made extremely slow by the usage of EVAL, and the multiple numeric-to-character conversions that are required for that. The author might like to learn why good (i.e. neat, efficient, robust code) avoids using EVAL:

<https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval>

MATLAB Release Compatibility
Created with R2012a
Compatible with any release
Platform Compatibility
Windows macOS Linux
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