Using Dynamic Field Names :: Data Types (Programming)

Programming

Using Dynamic Field Names

The most common way to access the data in a structure is by specifying the name of the field that you want to reference. Another means of accessing structure data is to use dynamic field names. These names express the field as a variable expression that MATLAB evaluates at run-time. The dot-parentheses syntax shown here makes expression a dynamic field name:

```
structName.(expression)
```

Index into this field using the standard MATLAB indexing syntax. For example, to evaluate expression into a field name and obtain the values of that field at columns 1 through 25 of row 7, use

```
structName.(expression)(7,1:25)
```

Dynamic Field Names Example

The avgscore function shown below computes an average test score, retrieving information from the testscores structure using dynamic field names:

function avg = avgscore(testscores, student, first, last)
for k = first:last
   scores(k) = testscores.(student).week(k);
end
avg = sum(scores)/(last - first + 1);

You can run this function using different values for the dynamic field, student:

avgscore(testscores, 'Ann_Lane', 1, 20)
ans = 
   83.5000

avgscore(testscores, 'William_King', 1, 20)
ans = 
   92.1000

Accessing Data in Structure Arrays Finding the Size of Structure Arrays