This command will only show the number of boys baptized each year.

$1.$ What command would you use to extract just the counts of girls baptized? Try it$!$

Notice that the way R has printed these data is different. When we looked at the complete data frame,

we saw $82$ rows, one on each line of the display. These data are no longer structured in a table with other

variables, so they are displayed one right after another. Objects that print out in this way are called vectors;

they represent a set of numbers. R has added numbers in $[$brackets$]$ along the left side of the printout to

indicate locations within the vector. For example, $5218$ follows $[1],$ indicating that $5218$ is the first entry in

the vector. And if $[43]$ starts a line, then that would mean the first number on that line would represent the

$43$rd entry in the vector.

R has some powerful functions for making graphics. We can create a simple plot of the number of girls

baptized per year with the command

plot$($x $=$ arbuthnot$year, y $=$ arbuthnot$girls$)$

By default, R creates a scatterplot with each x$,$y pair indicated by an open circle. The plot itself should

appear under the Plots tab of the lower right panel of RStudio. Notice that the command above again looks

like a function, this time with two arguments separated by a comma. The first argument in the plot function

specifies the variable for the x$-$axis and the second for the y$-$axis. If we wanted to connect the data points

with lines, we could add a third argument, the letter l for line.

plot$($x $=$ arbuthnot$year, y $=$ arbuthnot$girls, type $="$l$")$

You might wonder how you are supposed to know that it was possible to add that third argument. Thankfully,

R documents all of its functions extensively. To read what a function does and learn the arguments that are

available to you, just type in a question mark followed by the name of the function that you$$re interested in$.$

Try the following.

$?$plot

Notice that the help file replaces the plot in the lower right panel. You can toggle between plots and help

files using the tabs at the top of that panel.

$2.$ Is there an apparent trend in the number of girls baptized over the years?

How would you describe it$?$

Now, suppose we want to plot the total number of baptisms. To compute this, we could use the fact that R

is really just a big calculator. We can type in mathematical expressions like

$5218+4683$

to see the total number of baptisms in $1629.$ We could repeat this once for each year, but there is a faster

way. If we add the vector for baptisms for boys and girls, R will compute all sums simultaneously.

arbuthnot$boys $+$ arbuthnot$girls

What you will see are $82$ numbers $($in that packed display, because we aren$$t looking at a data frame here$),$

each one representing the sum we$$re after. Take a look at a few of them and verify that they are right.

Therefore, we can make a plot of the total number of baptisms per year with the command

plot$($arbuthnot$year, arbuthnot$boys $+$ arbuthnot$girls, type $="$l$")$

This time, note that we left out the names of the first two arguments. We can do this because the help file

shows that the default for plot is for the first argument to be the x$-$variable and the second argument to

be the y$-$variable. Similarly to how we computed the proportion of boys, we can compute the ratio of the

number of boys to the number of girls baptized in $1629$ with

$3$