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## Control Whether a Cell Array Is Variable-Size

The code generator classifies a variable-size cell array as homogeneous. The cell array elements must have the same class. In the generated code, the cell array is represented as an array.

To make a cell array variable-size:

• Create the cell array by using the `cell` function. For example:

```function z = mycell(n, j) %#codegen assert (n < 100); x = cell(1,n); for i = 1:n x{i} = i; end z = x{j}; end ```

For code generation, when you create a variable-size cell array by using `cell`, you must adhere to certain restrictions. See Definition of Variable-Size Cell Array by Using cell.

• Grow the cell array. For example:

```function z = mycell(n) %#codegen c = {1 2 3}; if n > 3 c = {1 2 3 4}; end z = c{n}; end```

• Force the cell array to be variable-size by using `coder.varsize`. Consider this code:

```function y = mycellfun() %#codegen c = {1 2 3}; coder.varsize('c', [1 10]); y = c{1}; end```

Without `coder.varsize`, `c` is fixed-size with dimensions 1-by-3. With `coder.varsize`, `c` is variable-size with an upper bound of 10.

Sometimes, using `coder.varsize` changes the classification of a cell array from heterogeneous to homogeneous. Consider this code:

```function y = mycell() %#codegen c = {1 [2 3]}; y = c{2}; end```

The code generator classifies `c` as heterogeneous because the elements have different sizes. `c` is fixed-size with dimensions 1-by-2. If you use `coder.varsize` with `c`, it becomes homogeneous. For example:

```function y = mycell() %#codegen c = {1 [2 3]}; coder.varsize('c', [1 10], [0 1]); y = c{2}; end```

`c` becomes a variable-size homogeneous cell array with dimensions 1-by-:10.

To force `c` to be homogeneous, but not variable-size, specify that none of the dimensions vary. For example:

```function y = mycell() %#codegen c = {1 [2 3]}; coder.varsize('c', [1 2], [0 0]); y = c{2}; end```

## Support

#### Model-Based Design for Embedded Control Systems

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