When working with matrices in Julia, it is common to construct them using the cat function. However, there may be cases where you want to construct a matrix without concatenating any arrays. In this article, we will explore three different ways to achieve a non-catting version of matrix construction in Julia.

## Option 1: Using the zeros function

The first option is to use the zeros function to create a matrix of the desired size filled with zeros. You can then assign values to specific elements of the matrix using indexing.

```
# Example code
n = 3
m = 4
A = zeros(n, m)
A[1, 1] = 1
A[2, 3] = 2
A[3, 2] = 3
```

This option is simple and straightforward. However, it may not be efficient if you need to assign values to a large number of elements in the matrix.

## Option 2: Using the fill function

The second option is to use the fill function to create a matrix filled with a specific value. You can then replace the desired elements with the values you want.

```
# Example code
n = 3
m = 4
A = fill(0, n, m)
A[1, 1] = 1
A[2, 3] = 2
A[3, 2] = 3
```

This option is similar to the first one, but it allows you to fill the matrix with a value other than zero. It can be useful if you want to initialize the matrix with a specific value.

## Option 3: Using a comprehension

The third option is to use a comprehension to construct the matrix. This allows you to specify the values of the elements directly in the comprehension.

```
# Example code
n = 3
m = 4
A = [i == j ? i : 0 for i in 1:n, j in 1:m]
```

This option is more concise and can be useful if you need to construct a matrix with a specific pattern or condition.

After exploring these three options, it is clear that the best choice depends on the specific requirements of your problem. If you need to assign values to a large number of elements, using the zeros or fill function may be more efficient. On the other hand, if you want to construct a matrix with a specific pattern or condition, using a comprehension can be a more concise solution.