Programming with MATLAB (Getting Started)

Getting Started

Structures

Structures are multidimensional MATLAB arrays with elements accessed by textual field designators. For example,

S.name = 'Ed Plum';
S.score = 83;
S.grade = 'B+'

creates a scalar structure with three fields.

S = 
     name: 'Ed Plum'
    score: 83
    grade: 'B+'

Like everything else in MATLAB, structures are arrays, so you can insert additional elements. In this case, each element of the array is a structure with several fields. The fields can be added one at a time,

S(2).name = 'Toni Miller';
S(2).score = 91;
S(2).grade = 'A-';

or an entire element can be added with a single statement.

S(3) = struct('name','Jerry Garcia',...
               'score',70,'grade','C')

Now the structure is large enough that only a summary is printed.

S = 
1x3 struct array with fields:
    name
    score
    grade

There are several ways to reassemble the various fields into other MATLAB arrays. They are all based on the notation of a comma-separated list. If you type

```
S.score
```

it is the same as typing

```
S(1).score, S(2).score, S(3).score
```

This is a comma-separated list. Without any other punctuation, it is not very useful. It assigns the three scores, one at a time, to the default variable ans and dutifully prints out the result of each assignment. But when you enclose the expression in square brackets,

```
[S.score]
```

it is the same as

```
[S(1).score, S(2).score, S(3).score]
```

which produces a numeric row vector containing all the scores.

```
ans =
    83    91    70
```

Similarly, typing

```
S.name
```

just assigns the names, one at a time, to ans. But enclosing the expression in curly braces,

```
{S.name}
```

creates a 1-by-3 cell array containing the three names.

ans = 
    'Ed Plum'    'Toni Miller'    'Jerry Garcia'

And

```
char(S.name)
```

calls the char function with three arguments to create a character array from the name fields,

ans =
Ed Plum    
Toni Miller
Jerry Garcia

Characters and Text Scripts and Functions