MATLAB String Array

4.1 String Array

4.1.1 getting started with strings

[* Example 4.1.1-1] First, ask the reader to perform actual operations in this example to see the difference between the numeric value and the string.
Clear % clear all memory Variables
A = 12345.6789% assign a numeric scalar to variable
Class (a) % determines the class of variable
A_s = size (a) % value array A's "size"
A =
1.22.16e + 004
Ans =
Double
A_s =
1 1

B ='s '% assigned variable B a character scalar (that is, a single character)
Class (B) % determines the type of variable B
B _s = size (B) % Represents the "size" of array B"
B =
S
Ans =
Char
B _s =
1 1
Whos % observe the bytes occupied by variables A and B in the memory
Name size bytes class
A 1x1 8 double Array
A_s 1X2 16 double Array
Ans 1X4 8 char array
B 1x1 2 char array
B _s 1X2 16 double Array
Grand total is 10 elements using 50 bytes

4.1.2 attributes and identifiers of string Arrays

[* Example 4.1.2-1] This example shows the basic attributes, identifiers, and simple operations of a string.

(1) create a String Array
A = 'this is an example .'
A =
This is an example.

(2) Size of String Array
Size ()
Ans =
1 19

(3) element ID of the string array
A14 = a () % raised a substring
Ra = a (end:-1:1) % inverted string
A14 =
This
Ra =
. Elpmaxe na Si siht

(4) ASCII code of the string array
Ascii_a = double (a) % generates ASCII code
Ascii_a =
Columns 1 through 12
84 104 105 115 32 105 115 32 97 110 32 101
Columns 13 through 19
120 97 109 112 108 46
Char (ascii_a) % returns the ASCII code back to the string
Ans =
This is an example.

(5) operations on the string ASCII code Array
% Uppercase letters in the string
W = find (A> = 'A' & A <= 'Z'); % locate the element location of lowercase letters in string array.
Ascii_a (w) = ascii_a (w)-32; % ASCII value difference between uppercase and lowercase letters 32. Use the value addition to change part of the code value.
Char (ascii_a) % converts the new ASCII code into characters
Ans =
This is an example.

(6) Chinese String Array
A = 'This is an example. '; % Create a Chinese String
A_s = size (a) % size of the string array
A56 = a ([5 6]) % obtain the sub-array of the string
Ascii_a = double (a) % get ASCII code
A_s =
1 7
A56 =

Example
Ascii_a =
Columns 1 through 6
54754 51911 53947 47350 52195 49405
Column 7
41379

Char (ascii_a) % translates ASCII code into characters
Ans =
This is an example.

(7) create a string with single quotes
B = 'example ''' 4.1.2-1 '''
B =
Example '4.1.2-1'

(8) A long string composed of small strings
AB = [A (), '', B, '.'] % here, the 2nd inputs are space strings.
AB =
This is example '4.1.2-1 '.

4.1.3 create a complex String Array

4.1.3.1 direct creation of multi-row string Arrays

[* Example 4.1.3. 1-1] direct input example of multi-line string array.
Clear
S = ['this string array'
'Has multiple rows. ']
S =
This string array
Has multiple rows.
Size (s)
Ans =
18

4.1.3.2 create multi-row string arrays using string operation functions

[* Example 4.1.3. 2-1] example: use special functions char, str2mat, and strvcat to create multi-row string array.
S1 = char ('this string array', 'has two rows .')
S1 =
This string array
Has two rows.
S2 = str2mat ('data', 'char', 'string' array, 'consists of 4 rows ')
S2 =
This
Character
String Array
Composed of four rows
S3 = strvcat
S3 =
This
Character
String Array
Composed of four rows
Size (S3)
Ans =
5 5

Supplement of [* example 4.1.3. 2-1]

(1) create a two-dimensional character array animal

> Animal = ['Dog'; 'monkey'];

??? Error Using ==> vertcat

Cat arguments dimensions are not consistent.

> Animal = ['Dog'; 'monkey']; % created successfully

Note: When creating a two-dimensional character array, each character array must contain the same column. When a multi-line string has different lengths, to avoid errors, you must add spaces to a short string to ensure the length of the short string and the longest string.

(2) create a character array using the char function. This method does not require the length of all strings.

> Animal = char ('dog ', 'monkey ');

4.1.3.3 conversion functions generate digital strings

[* Example 4.1.3. 3-1] int2str, num2str, and mat2str are the most common array/string conversion functions.

(1) int2str converts an integer array into a String Array (non-integers are rounded to the garden before conversion)
A = eye (2, 4); % generates a numerical array
A_str1 = int2str (a) % is converted into a string array. Please use the size test on your own.
A_str1 =
1 0 0 0
0 1 0 0

(2) num2str converts a non-integer array to a string array (commonly used in graphics, data point identification)
Rand ('state', 0)
B = rand (2, 4); % to generate a numerical Matrix
B3 = num2str (B, 3) % keep three valid digits and convert them to strings
B3 =
0.95 0.607 0.891 0.456
0.231 0.486 0.762 0.0185

(3) mat2str converts a numeric array into a string array in the input form (often with EVAl command configuration)
B _str = mat2str (B, 4) % to keep four valid digits and convert them to "array input form" strings
B _str =
[0.9501 0.6068 0.8913 0.4565; 0.2311 0.486 0.7621 0.0185]
ExprEssion = ['exp (-', B _str,') ']; % is equivalent to writing an expression exp (-B _str) in the Command window)
EVAl (exprEssion) % send exp (-B _str) to execute
Ans =
0.3867 0.5451 0.4101 0.6335
0.7937 0.6151 0.4667 0.9817

[* Example 4.1.3. 3-2] A comprehensive example is as follows: the plot name and the maximum coordinate are displayed on the graph generated by Matlab.
Clear % clear all variables in memory
A = 2; % set the attenuation coefficient
W = 3; % set the oscillation frequency
T = 0: 0. 0; % retrieved from the Variable Sampling Array
Y = exp (-A * t). * sin (w * t); % calculate the function value and generate the Function Array
[Y_max, I _max] = max (y); % locate the maximum element position
T_text = ['t =', num2str (T (I _max)]; % generate the x-axis string of the maximum vertex <7>
Y_text = ['y = ', num2str (y_max)]; % generate the ordinate string of the maximum vertex <8>
Max_text = char ('maximum ', t_text, y_text); % generate the string that marks the maximum value <9>
% String used to generate the logo image name
Tit = ['y = exp (-', num2str (A),'t) * sin (', num2str (W),'t) ']; % <11>
Plot (T, zeros (SIZE (t), 'k') % draw the baseline with the ordinate value 0
Hold on % keep drawn lines not cleared
Plot (T, Y, 'B') % plot Y (t) curve with blue
Plot (T (I _max), y_max, 'R. ', 'markersize', 20) % use a large red dot to mark the maximum Vertex
Text (T (I _max) + 0.3, y_max + 0.05, max_text) % write the data value of the maximum Vertex on the graph <16>
Title (tit), xlabel ('T'), ylabel ('y'), hold off % write image name, abscissa name, and ordinate name

Figure 4.1.3. 3-1 string usage

4.1.3.4 use the cellular array to create a complex string

[* Example 4.1.3. 4-1] The application of the cellular array in the storage and operation strings.
A = 'matlab 5'; B = 'introduces new DATa types: '; % create a single line string a, B
C1 = '◆ multimen=array'; C2 = '◆ user-definable daTa structure ';
C3 = '◆ cell arrays'; C4 = '◆ character array ';
C = char (C1, C2, C3, C4); % create multi-line string C
C = {A; B; C };%use the cellular array to store strings of different lengths <5>
Disp ([c {}]) % displays the characters in the first two cells <6>
Disp ('') % displays a blank line
Disp (c {3}) % displays the characters in the 3rd meta cells <8>
MATLAB 5 introduces new DATa types:
◆ Multidimen1_array
◆ User-definable daTa Structure
◆ Cell arrays
◆ Character array

4.1.4 String Conversion Function

[* Example 4.1.4-1] usage example of fprintf, sprintf, and sscanf.
Rand ('state', 0); A = rand (2, 2); % generates random arrays
S1 = num2str (a) % converts a numeric array to a String Array
S_s = sprintf ('%. 10E/N', A) % 10 digital scientific description string. Each element is written with a line feed.
S1 =
0.95013 0.60684
0.23114 0.48598
S_s =
9.5012928515e-001
2.3112131357e-001
6.0682138354e-001
4.8592136871e-001

Fprintf ('%. 5g //', a) % is displayed in the shortest form of 5 digits. Values cannot be assigned.
0.95013/0.23114/0.60684/0.48598/

S_sscan = sscanf (s_s, '% F', [3, 2]) % convert the string to a numerical array in floating-point format.
S_sscan =
0.9501 0.4860
0.2311 0

0.6068 0