Answers to the exercises are available here.

**Exercise 1**

What is the output of:

`ifelse(sqrt(9)<2,sqrt(9),0)`

**Exercise 2**

What is the output of:

`ifelse(sqrt(100)>9,sqrt(100),0)`

**Exercise 3**

What is the output `y`

of:

`x=12`

`if(is.numeric(x)) y=x*2`

**Exercise 4**

What is the output `x,y`

of:

`z=-1`

`if(z<0){x=abs(z);y=z*3}`

**Exercise 5**

What is the output `y`

of:

`z=6`

`if(z<0) y=z*3 else y=z*5`

**Exercise 6**

What is the output `z`

of:

`x=15`

`y=3`

`if(is.numeric(x))`

if(is.numeric(y) & y!=0)

z=x/y

**Exercise 7**

What is the output of:

`x=letters[20]`

`if (is.numeric(x)) print('is numeric') else`

if(is.character(x)) print('is character')

**Exercise 8**

What is the output of:

x=90

ifelse(x<100,ifelse(x/2==trunc(x/2),x/2,0),

ifelse(x/100==trunc(x/100),x/100,-1))

`x=120`

ifelse(x<100,ifelse(x/2==trunc(x/2),x/2,0),

ifelse(x/100==trunc(x/100),x/100,-1))

`x=200`

ifelse(x<100,ifelse(x/2==trunc(x/2),x/2,0),

ifelse(x/100==trunc(x/100),x/100,-1))

**Exercise 9**

What is the output `n`

of:

z='i'

if (z %in% letters)

if (z=='a') n=1 else

if (z=='e') n=2 else

if (z=='i') n=3 else

if (z=='o') n=4 else n=5

**Exercise 10**

What is the output `n`

of:

z='u'

if (z %in% letters)

if (z=='a') n=1 else

if (z=='e') n=2 else

if (z=='i') n=3 else

if (z=='o') n=4 else n=5

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