Creating a character string is quite simple in MATLAB. In fact, we have used it many times. For example, you type the following in the command prompt −
my_string = 'Tutorials Point'MATLAB will execute the above statement and return the following result −
my_string = Tutorials Point
MATLAB considers all variables as arrays, and strings are considered as character arrays. Let us use the whos command to check the variable created above −
whosMATLAB will execute the above statement and return the following result −
Name Size Bytes Class Attributes
my_string 1x16 32 char
Interestingly, you can use numeric conversion functions like uint8 or uint16 to convert the characters in the string to their numeric codes. The char function converts the integer vector back to characters −
Example
Create a script file and type the following code into it −
my_string = 'Tutorial''s Point';
str_ascii = uint8(my_string) % 8-bit ascii values
str_back_to_char= char(str_ascii)
str_16bit = uint16(my_string) % 16-bit ascii values
str_back_to_char = char(str_16bit) When you run the file, it displays the following result −
str_ascii =
84 117 116 111 114 105 97 108 39 115 32 80 111 105 110 116
str_back_to_char = Tutorial's Point
str_16bit =
84 117 116 111 114 105 97 108 39 115 32 80 111 105 110 116
str_back_to_char = Tutorial's Point
Rectangular Character Array
The strings we have discussed so far are one-dimensional character arrays; however, we need to store more than that. We need to store more dimensional textual data in our program. This is achieved by creating rectangular character arrays.
Simplest way of creating a rectangular character array is by concatenating two or more one-dimensional character arrays, either vertically or horizontally as required.
You can combine strings vertically in either of the following ways −
- Using the MATLAB concatenation operator [] and separating each row with a semicolon (;). Please note that in this method each row must contain the same number of characters. For strings with different lengths, you should pad with space characters as needed.
- Using the char function. If the strings are of different lengths, char pads the shorter strings with trailing blanks so that each row has the same number of characters.
Example
Create a script file and type the following code into it −
doc_profile = ['Zara Ali '; ...
'Sr. Surgeon '; ...
'R N Tagore Cardiology Research Center']
doc_profile = char('Zara Ali', 'Sr. Surgeon', ...
'RN Tagore Cardiology Research Center')When you run the file, it displays the following result −
doc_profile =
Zara Ali
Sr. Surgeon
R N Tagore Cardiology Research Center
doc_profile =
Zara Ali
Sr. Surgeon
RN Tagore Cardiology Research Center
You can combine strings horizontally in either of the following ways −
- Using the MATLAB concatenation operator, [] and separating the input strings with a comma or a space. This method preserves any trailing spaces in the input arrays.
- Using the string concatenation function, strcat. This method removes trailing spaces in the inputs.
Example
Create a script file and type the following code into it −
name = 'Zara Ali ';
position = 'Sr. Surgeon ';
worksAt = 'R N Tagore Cardiology Research Center';
profile = [name ', ' position ', ' worksAt]
profile = strcat(name, ', ', position, ', ', worksAt)When you run the file, it displays the following result −
profile = Zara Ali , Sr. Surgeon , R N Tagore Cardiology Research Center
profile = Zara Ali,Sr. Surgeon,R N Tagore Cardiology Research Center
Combining Strings into a Cell Array
From our previous discussion, it is clear that combining strings with different lengths could be a pain as all strings in the array has to be of the same length. We have used blank spaces at the end of strings to equalize their length.
However, a more efficient way to combine the strings is to convert the resulting array into a cell array.
MATLAB cell array can hold different sizes and types of data in an array. Cell arrays provide a more flexible way to store strings of varying length.
The cellstr function converts a character array into a cell array of strings.
Example
Create a script file and type the following code into it −
name = 'Zara Ali ';
position = 'Sr. Surgeon ';
worksAt = 'R N Tagore Cardiology Research Center';
profile = char(name, position, worksAt);
profile = cellstr(profile);
disp(profile)When you run the file, it displays the following result −
{
[1,1] = Zara Ali
[2,1] = Sr. Surgeon
[3,1] = R N Tagore Cardiology Research Center
}
String Functions in MATLAB
MATLAB provides numerous string functions creating, combining, parsing, comparing and manipulating strings.
Following table provides brief description of the string functions in MATLAB −
| Function | Purpose |
|---|---|
| Functions for storing text in character arrays, combine character arrays, etc. | |
| blanks | Create string of blank characters |
| cellstr | Create cell array of strings from character array |
| char | Convert to character array (string) |
| iscellstr | Determine whether input is cell array of strings |
| ischar | Determine whether item is character array |
| sprintf | Format data into string |
| strcat | Concatenate strings horizontally |
| strjoin | Join strings in cell array into single string |
| Functions for identifying parts of strings, find and replace substrings | |
| ischar | Determine whether item is character array |
| isletter | Array elements that are alphabetic letters |
| isspace | Array elements that are space characters |
| isstrprop | Determine whether string is of specified category |
| sscanf | Read formatted data from string |
| strfind | Find one string within another |
| strrep | Find and replace substring |
| strsplit | Split string at specified delimiter |
| strtok | Selected parts of string |
| validatestring | Check validity of text string |
| symvar | Determine symbolic variables in expression |
| regexp | Match regular expression (case sensitive) |
| regexpi | Match regular expression (case insensitive) |
| regexprep | Replace string using regular expression |
| regexptranslate | Translate string into regular expression |
| Functions for string comparison | |
| strcmp | Compare strings (case sensitive) |
| strcmpi | Compare strings (case insensitive) |
| strncmp | Compare first n characters of strings (case sensitive) |
| strncmpi | Compare first n characters of strings (case insensitive) |
| Functions for changing string to upper- or lowercase, creating or removing white space | |
| deblank | Strip trailing blanks from end of string |
| strtrim | Remove leading and trailing white space from string |
| lower | Convert string to lowercase |
| upper | Convert string to uppercase |
| strjust | Justify character array |
Examples
The following examples illustrate some of the above-mentioned string functions −
Formatting Strings
Create a script file and type the following code into it −
A = pi*1000*ones(1,5);
sprintf(' %f \n %.2f \n %+.2f \n %12.2f \n %012.2f \n', A)When you run the file, it displays the following result −
ans = 3141.592654
3141.59
+3141.59
3141.59
000003141.59
Joining Strings
Create a script file and type the following code into it −
%cell array of strings
str_array = {'red','blue','green', 'yellow', 'orange'};
% Join strings in cell array into single string
str1 = strjoin(str_array, "-")
str2 = strjoin(str_array, ",")When you run the file, it displays the following result −
str1 = red-blue-green-yellow-orange
str2 = red,blue,green,yellow,orange
Finding and Replacing Strings
Create a script file and type the following code into it −
students = {'Zara Ali', 'Neha Bhatnagar', ...
'Monica Malik', 'Madhu Gautam', ...
'Madhu Sharma', 'Bhawna Sharma',...
'Nuha Ali', 'Reva Dutta', ...
'Sunaina Ali', 'Sofia Kabir'};
% The strrep function searches and replaces sub-string.
new_student = strrep(students(8), 'Reva', 'Poulomi')
% Display first names
first_names = strtok(students)When you run the file, it displays the following result −
new_student =
{
[1,1] = Poulomi Dutta
}
first_names =
{
[1,1] = Zara
[1,2] = Neha
[1,3] = Monica
[1,4] = Madhu
[1,5] = Madhu
[1,6] = Bhawna
[1,7] = Nuha
[1,8] = Reva
[1,9] = Sunaina
[1,10] = Sofia
}
Comparing Strings
Create a script file and type the following code into it −
str1 = 'This is test'
str2 = 'This is text'
if (strcmp(str1, str2))
sprintf('%s and %s are equal', str1, str2)
else
sprintf('%s and %s are not equal', str1, str2)
endWhen you run the file, it displays the following result −
str1 = This is test
str2 = This is text
ans = This is test and This is text are not equal
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