Question $6$: Sequences

$1.$ Use the seq$()$ function to create a sequence of numbers ranging from $0$ to $1$ in steps of $0\mathrm{.}1($this is also

a vector by the way$)$ and assign this sequence to a variable called seq$1.$

$2.$ Next, create a sequence from $10$ to $1$ in steps of $0\mathrm{.}5$ and assign to a variable called seq$2($Hint: you

may find it easier to include the rev$()$ function in your code$).$

Ok$,$ just for fun, run the following code which shows how we can create all different kinds of patterns using

the rep$()$ function such as:

$123123123$

$$a$$a$$a$$c$$c$$c$$e$$e$$e$$g$$g$$g$$

$$a$$c$$e$$g$$a$$c$$e$$g$$a$$c$$e$$g$$

$111222333111222333$

$111112222333445$

$4$ sevens, $3$ twos, $1$ eight and $5$ ones

rep$(1$:$3,$ times $=3)$

rep$($c$("$a$","$c$","$e$","$g$"),$ each $=3)$

rep$($c$("$a$","$c$","$e$","$g$"),$ times $=3)$

rep$(1$:$3,$ each $=3,$ times $=2)$

rep$(1$:$5,$ times $=5$:$1)$

rep$($c$(7,2,8,1),$ times $=$ c$(4,3,1,5))$

Question $7$: Ordering

Say we have three kids $($John$,$ Jack, and Jane$)$ that are $63,59,$ and $60$ inches respectively. We can apply the

following code to order the heights from shortest to tallest and use those results to sort the names based on

the height. Consequently, we can see that Jack is the shortest followed by Jane and then John.

# names and heights of $3$ kids

child$\_$names $<-$ c$("$John$",$ "Jack", "Jane"$)$

ht $<-$ c$(63,59,60)$

# get the indexes of the heights, smallest to tallest and sort the names based

# on these indexes

height$\_$ord $<-$ order$($ht$)$

names$\_$sort $<-$ child$\_$names$[$height$\_$ord$]$

names$\_$sort

## $[1]$ "Jack" "Jane" "John"

Knowing this, apply this same procedure to a larger group of kids.

$1.$ Create a vector of child$\_$names and hts $($in inches$)$ for the following $10$ children:

$1.$ Alfred: $62$

$2.$ Barbara: $58$

$3$

$3.$ James: $61$

$4.$ Jane: $61$

$5.$ John: $59$

$6.$ Judy: $64$

$7.$ Louise: $63$

$8.$ Mary: $61$

$9.$ Ronald: $60$

$10.$ William: $62$

$2.$ Who is the shortest?

$3.$ Who is the tallest child?

$4.$ If you lined up these kids based on their height, which kids would be standing next to Alfred?

Question $8$: Missing values

Almost there! In R$,$ missing values are usually represented with an NA$.$ Missing data can be tricky to deal

with in R $($and in statistics more generally$)$ and cause some surprising behavior when using some functions.

To explore this a little further let$$s create a vector called mydata with the values $2,4,1,6,8,5,$ NA$,4,7.$

Notice the value of the $7$th element of mydata is missing and represented with an NA$.$ Now use the mean$()$

function to calculate the mean of the values in mydata. What does R return? Confused? Next, take a look

at the help page for the function mean$().$ Can you figure out how to alter your use of the mean$()$ function

to calculate the mean without this missing value?