Manipulating strings defined with the new double quote option

I imported data into MATLAB and the data I want to get is has somehow been converted in a double quote string: "00:06:57" (the type is listed as 'string').

How do I address individual characters defined in such a string? MATLAB only seems to be able to look at the inside of strings with single quote (i.e. '00:06:57') where I could specify a range of characters (this doesn't work with the double quote string function.

I am frustrated! It seems like this should be so easy...but it is not.

s1='00:06:57'; s1(2:4) = '0:0'

while

s1="00:06:57"; s1(2:4) => produces 'index exceeds matrix dimension' error

[Jan]

Do not get frustrated too soon. Matlab's documentation is marvelous and you can find the required details e.g. here.

Answer 1

[Jiro Doke]

Read up on the documentation on "strings".

Create String Arrays

It's different from character arrays: Represent Text with Character and String Arrays

What James suggested is correct. If you want to manipulate the "string" as a "character array", you can extract it using {}. Then combine that with regular indexing () to extract individual characters.

>> str = "00:06:57"
str = 
    "00:06:57"
>> ch = str{1}
ch =
    '00:06:57'
>> ch_snippet = str{1}(2:4)
ch_snippet =
    '0:0'

[Eomzi Yang]

this also works when inserting apostrophe into a string

[Bart McCoy]

If new to strings and you want to see it in steps, I've broken this down a little more.

% If working with a single string object (array with only 1 string obj)
oneStr = "00:06:57";    % One string object (array of 1 string object)
ch = oneStr.char();     % Convert string obj to char array
ch = oneStr{1};         % Convert string obj #1 to char array 

% If working with an array of string objects, { } notation makes more sense
strArray =  [ "00:06:57", "00:07:23",  "00:08:19" ];   % Array of string objects
st = strArray(2)        % returns "00:07:23",  the 2nd string obj
ch = strArray(2).char() % returns '00:07:23',  a char array from the 2nd string obj
ch = strArray{2}        % returns '00:07:23',  a char array from the 2nd string obj
                        % much nicer!

ch(4:5)                 % Char array manipulation- returns '07'
strArray{2}(4:5)        % Combining the last 2 steps without the intermediate 'ch'
                        % Also returns '07'

A key point is that a "string" is an object and you manipulate it (extract substrings, etc) using its methods. An array of string objects is an array of completely different strings, not an array of chars.

Characters are single char objects. It takes a char array to make something that looks like a string.

Answer 2

[James Tursa]

extractBetween(s1,2,4)

Answer 3

[John D'Errico]

Too late, but so what? An alternative is:

S = "234"
S = 
    "234"

whos S
  Name      Size            Bytes  Class     Attributes
  S         1x1               132  string

See that we cannot index using (), because S is just one object.

S(1)
ans = 
    "234"

But try this:

S{1}(1)
ans =
    '2'

So we can index into a string.

When all else fails...

methods(S)
Methods for class string:

cellstr         count           erase           extractBetween  insertBefore    le              pad             reverse         startsWith      
char            double          eraseBetween    ge              ismissing       lower           plus            sort            strip           
compose         endsWith        extractAfter    gt              issorted        lt              replace         split           strlength       
contains        eq              extractBefore   insertAfter     join            ne              replaceBetween  splitlines      upper

Answer 4

[MATLAB_User]

Thanks to everyone who responded so quickly. That was amazingly fast!

It's hard to pick the best answer but I think that Steven Lord's answer helped me the most.

Answer 5

[John BG]

Hi MATLAB_User

this is John BG <mailto:[e-mail] [e-mail]>

you can use a range, don't miss '[' ']'

s1([2:4])
 =
    '0:0'

or indices

s1([3 6])
=
    '::'

To get the figures only

s1(find(s1~=':'))
 =
    '000657'

if you find this answer useful would you please be so kind to consider marking my answer as Accepted Answer?

To any other reader, if you find this answer useful please consider clicking on the thumbs-up vote link

thanks in advance

John BG

<mailto:[e-mail] [e-mail]>

[Jan]

I think I have written these comments before already. Did you delete your answer and posted it again?

• In the first case omitting the square brackets is more efficient, see https://www.mathworks.com/matlabcentral/answers/35676-why-not-use-square-brackets
• In s1(find(s1~=':')) the find can be omitted for using the faster logical indexing.
• The problem of the OP concerned the new string class, not char vectors, such that the indexing methods do not apply here.