Search for Text

To determine if text is present, use a function that returns logical values, likecontains,startsWith, orendsWith. Logical values of1correspond to true, and0corresponds to false.

txt ="she sells seashells by the seashore"; TF = contains(txt,"sea")

TF =logical1

Calculate how many times the text occurs using thecountfunction.

n = count(txt,"sea")

n = 2

To locate where the text occurs, use thestrfindfunction, which returns starting indices.

idx = strfind(txt,"sea")

idx =1×211 28

Find and extract text using extraction functions, such asextract,extractBetween,extractBefore, orextractAfter.

mid = extractBetween(txt,"sea","shore")

mid = "shells by the sea"

Optionally, include the boundary text.

mid = extractBetween(txt,"sea","shore","Boundaries","inclusive")

mid = "seashells by the seashore"

Find Text in Arrays

The search and replacement functions can also find text in multi-element arrays. For example, look for color names in several song titles.

songs = ["Yellow Submarine";"Penny Lane";"Blackbird"]; colors =["Red","Yellow","Blue","Black","White"]; TF = contains(songs,colors)

TF =3x1 logical array1 0 1

To list the songs that contain color names, use the logicalTFarray as indices into the originalsongsarray. This technique is calledlogical indexing.

colorful = songs(TF)

colorful =2x1 string"Yellow Submarine" "Blackbird"

Use the functionreplaceto replace text insongsthat matches elements ofcolorswith the string"Orange".

replace(songs,colors,"Orange")

ans =3x1 string"Orange Submarine" "Penny Lane" "Orangebird"

Match Patterns

Since R2020b

In addition to searching for literal text, like “sea” or “yellow”, you can search for text that matches a pattern. There are many predefined patterns, such asdigitsPatternto find numeric digits.

address ="123a Sesame Street, New York, NY 10128"; nums = extract(address,digitsPattern)

nums =2x1 string"123" "10128"

For additional precision in searches, you can combine patterns. For example, locate words that start with the character “S”. Use a string to specify the “S” character, andlettersPatternto find additional letters after that character.

pat ="S"+ lettersPattern; StartWithS = extract(address,pat)

StartWithS =2x1 string"Sesame" "Street"

For more information, seeBuild Pattern Expressions.