Find the starting indices for occurrences of patterns in a character vector.

First, create a character vector.

str = 'Find the starting indices of a pattern in a character vector';

Find the pattern in.

k = strfind(str,'in')

k = 1×4

     2    15    19    40

There are four instances of the pattern in str.

Find the pattern In.

k = strfind(str,'In')

k =

     []

Since strfind is case sensitive, the pattern is not found. k is an empty array.

Find the blank spaces in str.

k = strfind(str,' ')

k = 1×10

     5     9    18    26    29    31    39    42    44    54

There are ten blank spaces in str.

Find the starting indices for occurrences of a pattern in a cell array of character vectors.

Create a cell array of character vectors.

str = {'How much wood would a woodchuck chuck';
       'if a woodchuck could chuck wood?'};

Find the pattern wood in str.

idx = strfind(str,'wood')

idx=2×1 cell array
    {1x2 double}
    {1x2 double}

Examine the output cell array to find the instances of the pattern.

idx{:,:}

ans = 1×2

    10    23

ans = 1×2

     6    28

The pattern wood occurs at indices 10 and 23 in the first character vector and at indices 6 and 28 in the second character vector.

Find the occurrences of a pattern in a character vector. Force strfind to return the indices of those occurrences in a cell array. Then display the indices.

Create a character vector and find the occurrences of the pattern ain.

str = 'The rain in Spain.';
k = strfind(str,'ain','ForceCellOutput',true)

k = 1x1 cell array
    {1x2 double}

strfind returns a scalar cell that contains a numeric array, which contains indices of occurrences of the pattern ain in str. To access the numeric array within the cell, use curly braces.

k{1}

ans = 1×2

     6    15