Programming with MATLAB (Getting Started)

Getting Started

Characters and Text

Enter text into MATLAB using single quotes. For example,

```
s = 'Hello'
```

The result is not the same kind of numeric matrix or array we have been dealing with up to now. It is a 1-by-5 character array.

Internally, the characters are stored as numbers, but not in floating-point format. The statement

```
a = double(s)
```

converts the character array to a numeric matrix containing floating-point representations of the ASCII codes for each character. The result is

```
a =
    72    101    108    108    111
```

The statement

```
s = char(a)
```

reverses the conversion.

Converting numbers to characters makes it possible to investigate the various fonts available on your computer. The printable characters in the basic ASCII character set are represented by the integers 32:127. (The integers less than 32 represent nonprintable control characters.) These integers are arranged in an appropriate 6-by-16 array with

```
F = reshape(32:127,16,6)';
```

The printable characters in the extended ASCII character set are represented by F+128. When these integers are interpreted as characters, the result depends on the font currently being used. Type the statements

```
char(F)
char(F+128)
```

and then vary the font being used for the MATLAB Command Window. Select Preferences from the File menu. Be sure to try the Symbol and Wingdings fonts, if you have them on your computer. Here is one example of the kind of output you might obtain.

 !"#$%&'()*+,-./
0123456789:;<=>?
@ABCDEFGHIJKLMNO
PQRSTUVWXYZ[\]^_
`abcdefghijklmno
pqrstuvwxyz{|}~\x7f 

°¢§¶ß®©^TM´¨ÆØ
\xb0 ±¥µ¹²³½ªº¾æø
¿¡¬Ýý«»...þÀÃÕ
---""`'÷Þÿ\xd9 \xda ¤\xde \xdf 
·ÂÊÁËÈÍÎÏÌÓÔ
ÒÚÛÙ\xf5 ~¯\xf9 \xfa °¸\xfd \xfe \xff

Concatenation with square brackets joins text variables together into larger strings. The statement

```
h = [s, ' world']
```

joins the strings horizontally and produces

```
h =
   Hello world
```

The statement

```
v = [s; 'world']
```

joins the strings vertically and produces

```
v =
   Hello
   world
```

Note that a blank has to be inserted before the 'w' in h and that both words in v have to have the same length. The resulting arrays are both character arrays; h is 1-by-11 and v is 2-by-5.

To manipulate a body of text containing lines of different lengths, you have two choices--a padded character array or a cell array of strings. The char function accepts any number of lines, adds blanks to each line to make them all the same length, and forms a character array with each line in a separate row. For example,

S = char('A','rolling','stone','gathers','momentum.')

produces a 5-by-9 character array.

S =
A        
rolling  
stone    
gathers  
momentum.

There are enough blanks in each of the first four rows of S to make all the rows the same length. Alternatively, you can store the text in a cell array. For example,

C = {'A';'rolling';'stone';'gathers';'momentum.'}

is a 5-by-1 cell array.

C = 
    'A'
    'rolling'
    'stone'
    'gathers'
    'momentum.'

You can convert a padded character array to a cell array of strings with

```
C = cellstr(S)
```

and reverse the process with

```
S = char(C)
```

Cell Arrays Structures