# let¶

## Purpose¶

Creates a matrix from a list of numeric or character values. The result is always of type matrix, string, or string array.

## Format¶

```
let x = constant_list;
```

## Examples¶

```
let x;
```

assigns *x* to be:

```
x = 0
```

```
let x = { 1 2 3, 4 5 6, 7 8 9 };
```

assigns *x* to be:

```
1 2 3
x = 3 4 5
6 7 8
```

```
let x[3,3] = 1 2 3 4 5 6 7 8 9;
```

assigns *x* to be:

```
1 2 3
x = 3 4 5
6 7 8
```

```
let x[3,3] = 1;
```

assigns *x* to be:

```
1 1 1
x = 1 1 1
1 1 1
```

```
let x[3,3];
```

assigns *x* to be:

```
0 0 0
x = 0 0 0
0 0 0
```

```
let x = dog cat;
```

assigns *x* to be:

```
x = DOG
CAT
```

```
let x = "dog""cat";
```

assigns *x* to be:

```
x = dog
cat
```

```
let string x = { "Median Income", "Country" };
```

assigns *x* to be:

```
x = Median Income
Country
```

## Remarks¶

Expressions and variable names are not allowed in the let command, expressions such as this:

```
let x[2, 1] = 3*a b
```

are illegal. To define matrices by combining matrices and expressions,
use an expression containing the concatenation operators: `~`

and `|`

.

Numbers can be entered in scientific notation. The syntax is \(dE±n\), where
*d* is a number and *n* is an integer (denoting the power of 10):

```
let x = 1e+10 1.1e-4 4.019e+2;
```

Complex numbers can be entered by joining the real and imaginary parts with a sign (+ or -); there should be no spaces between the numbers and the sign. Numbers with no real part can be entered by appending an “i” to the number:

```
let x = 1.2+23 8.56i 3-2.1i -4.2e+6i 1.2e-4-4.5e+3i;
```

If curly braces are used, the let is optional.

```
let x = { 1 2 3, 4 5 6, 7 8 9 };
```

```
x = { 1 2 3, 4 5 6, 7 8 9 };
```

If indices are given, a matrix of that size will be created:

```
let x[2,2] = 1 2 3 4;
```

```
x = 1 2
3 4
```

If indices are not given, a column vector will be created:

```
let x = 1 2 3 4;
```

```
1
x = 2
3
4
```

You can create matrices with no elements, i.e., “empty matrices” . Just use a set of empty curly braces:

```
x = {};
```

Empty matrices are chiefly used as the starting point for building up a
matrix, for example in a `do`

loop. See Matrices for
more information on empty matrices.

Character elements are allowed in a let statement:

```
let x = age pay sex;
```

```
AGE
x = PAY
SEX
```

Lowercase elements can be created if quotation marks are used. Note that each element must be quoted.

```
let x = "age" "pay" "sex";
```

```
age
x = pay
sex
```