---
title: "Quiz 2 preparation solution"
output:
  word_document: default
  html_notebook: default
  pdf_document: default
---

Answer the following questions.

These questions relate to the homework problem 12.2.1 Exercise 2. Use what you know from Chapter
13 to answer the questions for *table4a* and *table4b*.

1. Using *table4a* and *table4b* from the *tidyverse* R package, merge the two dataframes into one and create
a column, rate per 10000 variable, for each year.

```{r message=FALSE}
library(tidyverse)
table4a
table4b
```


```{r}
table_new2 <- table4a %>% inner_join(table4b, by = c("country"))
table_new2
```

```{r}
table_new2a <- table_new2 %>% mutate(
rate.1999 = (`1999.x`/`1999.y`)*10000,
rate.2000 = (`2000.x`/`2000.y`)*10000
) %>%
select(country, rate.1999, rate.2000)
table_new2a
```

2. Is your final dataframe for questions 1 tidy? Yes or no, explain.

**Answer:** No.  The *table_new2a* is not tidy.  The rates are in two columns.

3. Convert your final dataframe for question 1 into a tidy dataframe with three columns country, year
and rate.

**Answer:**  Gather the columns into year and rate columns.

```{r}
table_new2a %>% gather(rate.1999, rate.2000, key = "year", value = "rate")
```

4. Make a clustered bar graph displaying the data.

Note the use of the as.factor() function.

```{r}
table_new2a %>% gather(rate.1999, rate.2000, key = "year", value = "rate") %>%
  ggplot(aes(x = as.factor(year), y = rate, fill = country) ) +
  geom_bar(position="dodge", stat="identity")
```

The next question relates to Chapter 14.

```{r}
library(stringr)
```

5. For the string “Today is the second quiz.”

    a. Use an *str_?* R function to count the length of the string.

    b. Use an *str_* R function to change all of the letters to lower case.

    c. Use an *str_?* R function to subset the string into separate words.

```{r}
x <- "Today is the second quiz."
x

# a.
str_count(x)

# b.
str_to_lower(x)

# c.
str_split(x, " ")

```