r-quiz

R

en

quiz

Published

March 11, 2024

1 Define a variable

Exercise
Solution

Define in R the variable age and assign the value 42.

age <- 42

Note that spaces here are not mandatory, but useful.

2 Define a variable as a string

Exercise
Solution

Define in R the variable name and assign the value me.

name <- "me"

3 Define a variable by another variable

Exercise
Solution

Define in R the variable name and assign the variable age.

name <- age

4 Call a function

Exercise
Solution

Ask R what today’s date() is, that is, call a function.

date()

[1] "Mon Mar 11 12:38:04 2024"

5 Define a vector

Exercise
Solution

Define in R a vector x with the values 1,2,3 .

x <- c(1, 2, 3)

6 Sum up vector

Exercise
Solution

Define in R a vector x with the values 1,2,3 . Then sum up its values.

x <- c(1, 2, 3)
sum(x)

[1] 6

7 Vector wise computation

Exercise
Solution

Square each value in the vector x.

x^2

[1] 1 4 9

8 Vector wise computation 2

Exercise
Solution

Square each value in the vector x and sum up the values.

sum(x^2)

[1] 14

9 Compute the variance

Exercise
Solution

Compute the variance of x using basic arithmetic.

 x <- c(1, 2, 3)

sum((x - mean(x))^2) / (length(x)-1)

[1] 1

 # compare: 
var(x)

[1] 1

10 Work with NA

Exercise
Solution

Define the vector y with the values 1,2,NA. Compute the mean. Explain the results.

y <- c(1, 2, NA)
mean(y)

[1] NA

NA (not available, ie., missing data) is contagious in R: If there’s a missing element, R will assume that something has gone wrong and will raise a red flag, i.e, give you a NA back.

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date: 2024-03-11
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title: r-quiz 

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## Define a variable

:::{.panel-tabset}

## Exercise

Define in R the variable `age` and assign the value `42`.

## Solution


```{r}
age <- 42
```

Note that spaces here are not mandatory, but useful.

:::


## Define a variable as a string
:::{.panel-tabset}

## Exercise

Define in R the variable `name` and assign the value `me`.


## Solution


```{r}
name <- "me"
```
:::


## Define a variable by another variable
:::{.panel-tabset}

## Exercise

Define in R the variable `name` and assign the *variable* `age`.

## Solution 


```{r}
name <- age
```
:::

## Call a function
:::{.panel-tabset}

## Exercise
Ask R what today's  `date()` is, that is, call a function.


## Solution 


```{r}
date()
```
:::

## Define a vector
:::{.panel-tabset}
## Exercise
Define in R a vector `x` with the values 1,2,3 . 

## Solution 
```{r}
x <- c(1, 2, 3)
```
:::



## Sum up vector
:::{.panel-tabset}
## Exercise
Define in R a vector `x` with the values 1,2,3 . Then sum up its values.

## Solution 
```{r}
x <- c(1, 2, 3)
sum(x)
```
:::

## Vector wise computation
:::{.panel-tabset}
## Exercise
Square each value in the vector `x`.


## Solution

```{r}
x^2
```

:::


## Vector wise computation 2
:::{.panel-tabset}

## Exercise

Square each value in the vector `x` and sum up the values.

## Solution

```{r}
sum(x^2)
```

:::


## Compute the variance
:::{.panel-tabset}


## Exercise

Compute the variance of `x` using basic arithmetic.

## Solution

```{r}
 x <- c(1, 2, 3)

sum((x - mean(x))^2) / (length(x)-1)

 # compare: 
var(x) 
```

:::

## Work with NA
:::{.panel-tabset}


## Exercise

Define the vector `y` with the values 1,2,NA. Compute the mean. Explain the results.

## Solution

```{r}
y <- c(1, 2, NA)
mean(y)
```


`NA` (not available, ie., missing data) is contagious in R: If there's a missing element, R will assume that something has gone wrong and will raise a red flag, i.e, give you a NA back.
:::