# Section 7 - Performing Calculations

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## Creating Matrices in MATLAB

```my_scalar = 3.1415
```
```my_scalar =

3.1415

```
```my_vector1 = [1, 5, 7]
```
```my_vector1 =

1     5     7

```
```my_vector2 = [1; 5; 7]
```
```my_vector2 =

1
5
7

```
```my_matrix = [8, 12, 19; 7, 3, 2; 12, 4, 23; 8, 1, 1]
```
```my_matrix =

8    12    19
7     3     2
12     4    23
8     1     1

```
```row_vector1 = [1 2 3]
```
```row_vector1 =

1     2     3

```
```row_vector2 = [3 2 1]
```
```row_vector2 =

3     2     1

```
```matrix_from_row_vec = [row_vector1 ; row_vector2]
```
```matrix_from_row_vec =

1     2     3
3     2     1

```
```column_vector1 = [1;3]
```
```column_vector1 =

1
3

```
```column_vector2 = [2;8]
```
```column_vector2 =

2
8

```
```matrix_from_col_vec = [column_vector1 column_vector2]
```
```matrix_from_col_vec =

1     2
3     8

```
```my_matrix = [8, 12, 19; 7, 3, 2; 12, 4, 23; 8, 1, 1]
```
```my_matrix =

8    12    19
7     3     2
12     4    23
8     1     1

```
```combined_matrix = [my_matrix, my_matrix]
```
```combined_matrix =

8    12    19     8    12    19
7     3     2     7     3     2
12     4    23    12     4    23
8     1     1     8     1     1

```
```time = 0:100:2300
```
```time =

Columns 1 through 10

0         100         200         300         400         500         600         700         800         900

Columns 11 through 20

1000        1100        1200        1300        1400        1500        1600        1700        1800        1900

Columns 21 through 24

2000        2100        2200        2300

```
```time_dec = 2300:-100:0
```
```time_dec =

Columns 1 through 10

2300        2200        2100        2000        1900        1800        1700        1600        1500        1400

Columns 11 through 20

1300        1200        1100        1000         900         800         700         600         500         400

Columns 21 through 24

300         200         100           0

```

## Indexing Into a Matrix

```my_vector1 = [1 5 7]
```
```my_vector1 =

1     5     7

```
```my_vector2 = [1; 5; 7]
```
```my_vector2 =

1
5
7

```
```my_vector1(1)
```
```ans =

1

```
```my_vector2(2)
```
```ans =

5

```
```my_vector1(3)
```
```ans =

7

```
```my_vector2(1)
```
```ans =

1

```
```my_vector2(2)
```
```ans =

5

```
```my_vector2(3)
```
```ans =

7

```
```my_matrix = [8, 12, 19; 7, 3, 2; 12, 4, 23; 8, 1, 1]
```
```my_matrix =

8    12    19
7     3     2
12     4    23
8     1     1

```
```my_matrix(3,2)
```
```ans =

4

```
```mat = [1  8 9 4 5 2 4 8
9  3 7 4 8 2 8 8
1  2 9 4 6 2 3 4
10  2 2 4 6 7 3 2
3 12 3 3 2 8 4 9]
```
```mat =

1     8     9     4     5     2     4     8
9     3     7     4     8     2     8     8
1     2     9     4     6     2     3     4
10     2     2     4     6     7     3     2
3    12     3     3     2     8     4     9

```
```new_mat = mat(2:4,4:7)
```
```new_mat =

4     8     2     8
4     6     2     3
4     6     7     3

```
```new_mat
```
```new_mat =

4     8     2     8
4     6     2     3
4     6     7     3

```
```new_mat(2,3) = 1999
```
```new_mat =

4           8           2           8
4           6        1999           3
4           6           7           3

```