Lab 2B

Directions: Follow along with the slides and answer the questions in **red** font in your journal.

- Means, medians, and MAD are just a few examples of
*numerical summaries*. - In this lab, we will learn how to calculate and interpret additional summaries of distributions such as: minimums, maximums, ranges, quartiles and IQRs.
- We’ll also learn how to write our first custom function!

- Start by loading your
*Personality Color*data again and name it`colors`

.

- Besides looking at
*typical*values, sometimes we want to see*extreme*values, like the smallest and largest values.- To find these values, we can use the
`min`

,`max`

or`range`

functions. These functions use a similar syntax as the`mean`

function.

- To find these values, we can use the
**Find the**`min`

value and`max`

value for your predominant color.**Apply the**`range`

function to your predominant color and describe the output.- The
*range*of a variable is the difference between a variable’s smallest and largest value. - Notice, however, that our
`range`

function calculates the maximum and minimum values for a variable, but not the difference between them. - Later in this lab you will create a custom
`Range`

function that will calculate the difference.

- The

- The
*median*of our data is the value that splits our data in half.- Half of our data is smaller than the
*median*, half is larger.

- Half of our data is smaller than the
*Q1*and*Q3*are similar.- 25% of our data is smaller than
*Q1*, 75% are larger.

- 25% of our data is smaller than
- Fill in the blanks to compute the value of
*Q1*for your predominant color.

**Use a similar line of code to calculate***Q3*, which is the value that’s larger than 75% of our data.

- Make a
`dotPlot`

of your*predominant*color’s scores. Make sure to include the`nint`

option. - Visually (Don’t worry about being super-precise):
- Cut the distribution into quarters so the
*number*of*data points*is equal for each piece. (Each piece should contain 25% of the data.)- Hint: You might consider using the
`add_line(vline = )`

to add vertical lines at the quarter marks.

- Hint: You might consider using the
**Write down the numbers that split the data up into these 4 pieces.****How long is the interval of the middle two pieces?**- This length is the
*IQR*.

- Cut the distribution into quarters so the

- The
`IQR`

is another way to describe*spread*.- It describes how
*wide*or*narrow*the middle 50% of our data are.

- It describes how
- Just like we used the
`min`

and`max`

to compute the`range`

, we can also use the*1st*and*3rd*quartiles to compute the*IQR*. **Use the values of**.*Q1*and*Q3*you calculated previously for your predominant color and find the*IQR*by hand**Then use the**`iqr()`

function to calculate it for you.

**Which personality color score has the widest spread according to the***IQR*? Which is narrowest?

- By using the medians, quartiles, and min/max, we can construct a new single variable plot called the
*box and whisker*plot, often shortened to just*boxplot*. **By showing someone a**`dotPlot`

, how would you teach them to make a*boxplot*? Write out your explanation in a series of steps for the person to use.**Use the steps you write to create a sketch of a***boxplot*for your predominant color’s scores in your journal.**Then use the**`bwplot`

function to create a*boxplot*using`R`

.

- In the past two labs, we’ve learned how to calculate numerous
*numerical summaries*.- Computing lots of different summaries can be tedious.

- Fill in the blanks below to compute some of our
*favorite*summaries for your predominant color all at once.

- We saw in a previous slide that the
`range`

function calculates the maximum and minimum values for a variable, but not the difference between them. - We could calulate this difference in two steps:
- Step 1: Use the
`range`

function to`assign`

the max and min values of a variable the name`values`

. This will store the output from the`range`

function in the*environment*pane.

- Step 1: Use the

- Step 2: Use the
`diff`

function to calculate the difference of`values`

. The input for the`diff`

function needs to be a vector containig two numeric values.

**Use these two steps to calculate the***range*of your predominant color.

- Calculating the
*range*of many variables can be tedious if we have to keep performing the same two steps over and over.- We can combine these two steps into one by writing our own custom
`function`

.

- We can combine these two steps into one by writing our own custom
- Custom functions can be used to combine a task that would normally take many steps to compute and simplify them into one.
- The next slide shows an example of how we can create a custom function called
`mm_diff`

to calculate the absolute difference between the`mean`

and`median`

value of a`variable`

in our`data`

.

```
mm_diff <- function(variable, data) {
mean_val <- mean(variable, data = data)
med_val <- median(variable, data = data)
abs(mean_val - med_val)
}
```

- The function takes two
*generic*arguments:`variable`

and`data`

- It then follows the steps between the curly braces
`{}`

- Each of the
*generic*arguments is used inside the`mean`

and`median`

functions.

- Each of the
- Copy and paste the code above into a
*R script*and*run*it. - The
`mm_diff`

function will appear in your*Environment*pane.

- After running the code used to create the function, we can use it just like we would any other numerical summary.
- In the
*console*, fill in the blanks below to calculate the absolute difference between the`mean`

and`median`

values of your predominant color:

- In the

**Which of the four colors has the largest absolute difference between the**`mean`

and`median`

values?**By examining a**`dotPlot`

for this personality color, make an argument why either the`mean`

or`median`

would be the better description of the*center*of the data.

- Using the previous example as a guide, create a function called
`Range`

(*Note the capital ‘R’*) that calculates the*range*of a variable by filling in the blanks below:

**Use the**`Range`

function to find the personality color with the largest difference between the`max`

and`min`

values.

**Create a function called**`myIQR`

that uses the`quantile`

function to compute the middle 30% of the data.