# Matrix Vol. 2 Exercises

**R-exercises**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)

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[For this exercise, first write down your answer, without using R. Then, check your answer using R.]

Answers to the exercises are available here.

**Exercise 1**

If

`M=matrix(c(1:10),nrow=5,ncol=2,`

```
```

`dimnames=list(c('a','b','c','d','e'),c('A','B')))`

What is the value of: `M`

**Exercise 2**

Consider the matrix `M`

,

What is the value of:

`M[1,]`

`M[,1]`

`M[3,2]`

`M['e','A']`

**Exercise 3**

Consider the matrix `N`

`N=matrix(c(1:9),nrow=3,ncol=3,`

```
```dimnames=list(c('a','b','c'),c('A','B','C')))

What is the value of: `diag(N)`

**Exercise 4**

What is the value of: `diag(4,3,3)`

Is matrix ?

**Exercise 5**

If `M=matrix(c(1:9),3,3,byrow=T,`

```
```

`dimnames=list(c('a','b','c'),c('d','e','f')))`

What is the value of:

`rownames(M)`

`colnames(M)`

**Exercise 6**

What is the value of:

`upper.tri(M)`

`lower.tri(M)`

`lower.tri(M,diag=T)`

**Exercise 7**

Consider two matrix,

`M,N`

```
```

`M=matrix(c(1:9),3,3,byrow=T)`

`N=matrix(c(1:9),3,3)`

```
```

What is the value of:

`M*N`

```
```

**Exercise 8**

Consider two matrix,

`M,N`

```
```

`M=matrix(c(1:9),3,3,byrow=T)`

`N=matrix(c(1:9),3,3)`

```
```

What is the value of:

`M%*%N`

```
```

**Exercise 9**

Consider two matrix,

`M,N`

```
```

`M=matrix(c(1:9),3,3,byrow=T)`

`N=matrix(c(1:9),3,3)`

```
```

What is the value of:

`(M+N)^2`

**Exercise 10**

Consider two matrix,

`M,N`

```
```

`M=matrix(c(1:9),3,3,byrow=T)`

`N=matrix(c(1:9),3,3)`

```
```

What is the value of:

`M/N`

**Want to practice matrices a bit more? We have more exercise sets on this topic here.**

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**R-exercises**.

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