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• basic command for creating matrix:
```m <- matrix(data=c(1:20), nrow=4, ncol=5)
```

This command creates matrix as array with only 2 dimensions. If you print this matrix R gives you response:

```     [,1] [,2] [,3] [,4] [,5]
[1,]    1    5    9   13   17
[2,]    2    6   10   14   18
[3,]    3    7   11   15   19
[4,]    4    8   12   16   20
```
• but array can have more dimensions:
```m2 <- array(c(1:40), dim=c(4,5,2))
```

if we print it we see this:

```, , 1

[,1] [,2] [,3] [,4] [,5]
[1,]    1    5    9   13   17
[2,]    2    6   10   14   18
[3,]    3    7   11   15   19
[4,]    4    8   12   16   20

, , 2

[,1] [,2] [,3] [,4] [,5]
[1,]   21   25   29   33   37
[2,]   22   26   30   34   38
[3,]   23   27   31   35   39
[4,]   24   28   32   36   40
```

functions for manipulation with matrixes:

• nrow(), ncol() – number of rows/ columns
• dim() – return dimensions
• t() – transposition of the matrix
• diag – return leading diagonal
• sum(diag()) – sum of leading diagonal of the matrix
• %*% – matrix multiplication