6.4) The Cell Class

Cell arrays are very flexible arrays that can hold:

• values of different types - e.g. numeric and char data in different cells, or:
• sub-arrays of different sizes - and hence:
• multiple char vectors of different lengths (e.g. words and phrases).

So they typically store heterogeneous data or text strings (remember that a single text string is a char vector).

Cell arrays are indexed much like other arrays. However:

• We normally create a cell array using curly brackets. Then:
• If we access cell array elements using round brackets, we end up with a cell array containing the selected data. i.e., we end up with a subset of the array.
• To access a data value itself we must use curly brackets { }. This means we pull out the data within a cell container rather than the cell container itself. For example:
  [matlab]
  >> Days={'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'};
  >> First_Day=Days{1};
  >> First_Letter_Of_3rd_Day=Days{3}(1);
  % Note the use of { } and ( ). Days{3}='Wed'
  [/matlab]
• Of course, even if you want to store single-letter strings within an otherwise numeric array, you still need a cell array.

Cell arrays are used when elements of different types or sizes need to be stored in a single array. For greater flexibility (e.g. to combine multiple arrays as a single entity), you should use structures instead.

We will return to cell arrays later.