Data Wrangling II

class: center, middle, inverse, title-slide

# Data Wrangling II

---

Click the link below to create the repository for lecture notes #05
  - https://classroom.github.com/a/cy3k00Il
  
Follow the steps to clone the repo, make a new RStudio project, and configure
git. Change the author name in the YAML header of `lecture05.Rmd` to your name and
update the date to today's date.

<br>

Complete the Lab Team Formation Survey by 2-09 11:59 PM. Do this now if you 
have time.
 - [https://forms.gle/mZMZ53Zfy3yPHwdJ6](https://forms.gle/mZMZ53Zfy3yPHwdJ6)

---

class: center, middle

# Data Wrangling Quiz

---

### Question #1

.reallytiny[

```
## # A tibble: 234 x 11
##    manufacturer model    displ  year   cyl trans   drv     cty   hwy fl    class
##    <chr>        <chr>    <dbl> <int> <int> <chr>   <chr> <int> <int> <chr> <chr>
##  1 audi         a4         1.8  1999     4 auto(l… f        18    29 p     comp…
##  2 audi         a4         1.8  1999     4 manual… f        21    29 p     comp…
##  3 audi         a4         2    2008     4 manual… f        20    31 p     comp…
##  4 audi         a4         2    2008     4 auto(a… f        21    30 p     comp…
##  5 audi         a4         2.8  1999     6 auto(l… f        16    26 p     comp…
##  6 audi         a4         2.8  1999     6 manual… f        18    26 p     comp…
##  7 audi         a4         3.1  2008     6 auto(a… f        18    27 p     comp…
##  8 audi         a4 quat…   1.8  1999     4 manual… 4        18    26 p     comp…
##  9 audi         a4 quat…   1.8  1999     4 auto(l… 4        16    25 p     comp…
## 10 audi         a4 quat…   2    2008     4 manual… 4        20    28 p     comp…
## # … with 224 more rows
```
]

#### Wrangled Data

.reallytiny[

```
## # A tibble: 234 x 3
##     year   cty   hwy
##    <int> <int> <int>
##  1  1999    18    29
##  2  1999    21    29
##  3  2008    20    31
##  4  2008    21    30
##  5  1999    16    26
##  6  1999    18    26
##  7  2008    18    27
##  8  1999    18    26
##  9  1999    16    25
## 10  2008    20    28
## # … with 224 more rows
```
]

---

### Question #2

.reallytiny[

#### Wrangled Data

.reallytiny[

```
## # A tibble: 45 x 11
##    manufacturer model  displ  year   cyl trans   drv     cty   hwy fl    class  
##    <chr>        <chr>  <dbl> <int> <int> <chr>   <chr> <int> <int> <chr> <chr>  
##  1 audi         a4       1.8  1999     4 manual… f        21    29 p     compact
##  2 audi         a4       2    2008     4 auto(a… f        21    30 p     compact
##  3 chevrolet    malibu   2.4  2008     4 auto(l… f        22    30 r     midsize
##  4 honda        civic    1.6  1999     4 manual… f        28    33 r     subcom…
##  5 honda        civic    1.6  1999     4 auto(l… f        24    32 r     subcom…
##  6 honda        civic    1.6  1999     4 manual… f        25    32 r     subcom…
##  7 honda        civic    1.6  1999     4 manual… f        23    29 p     subcom…
##  8 honda        civic    1.6  1999     4 auto(l… f        24    32 r     subcom…
##  9 honda        civic    1.8  2008     4 manual… f        26    34 r     subcom…
## 10 honda        civic    1.8  2008     4 auto(l… f        25    36 r     subcom…
## # … with 35 more rows
```
]

---

### Question #3

.reallytiny[

#### Wrangled Data

.reallytiny[

```
## # A tibble: 234 x 11
##    manufacturer model   displ  year   cyl trans   drv     cty   hwy fl    class 
##    <chr>        <chr>   <dbl> <int> <int> <chr>   <chr> <int> <int> <chr> <chr> 
##  1 volkswagen   jetta     1.9  1999     4 manual… f        33    44 d     compa…
##  2 volkswagen   new be…   1.9  1999     4 manual… f        35    44 d     subco…
##  3 volkswagen   new be…   1.9  1999     4 auto(l… f        29    41 d     subco…
##  4 toyota       corolla   1.8  2008     4 manual… f        28    37 r     compa…
##  5 honda        civic     1.8  2008     4 auto(l… f        25    36 r     subco…
##  6 honda        civic     1.8  2008     4 auto(l… f        24    36 c     subco…
##  7 toyota       corolla   1.8  1999     4 manual… f        26    35 r     compa…
##  8 toyota       corolla   1.8  2008     4 auto(l… f        26    35 r     compa…
##  9 honda        civic     1.8  2008     4 manual… f        26    34 r     subco…
## 10 honda        civic     1.6  1999     4 manual… f        28    33 r     subco…
## # … with 224 more rows
```
]

---

### Question #4

.reallytiny[

#### Wrangled Data

.reallytiny[

```
## # A tibble: 22 x 3
##    manufacturer drv       n
##    <chr>        <chr> <int>
##  1 audi         4        11
##  2 audi         f         7
##  3 chevrolet    4         4
##  4 chevrolet    f         5
##  5 chevrolet    r        10
##  6 dodge        4        26
##  7 dodge        f        11
##  8 ford         4        13
##  9 ford         r        12
## 10 honda        f         9
## # … with 12 more rows
```
]

---

### Question #5

.reallytiny[

#### Wrangled Data

.reallytiny[

```
## # A tibble: 234 x 12
##    manufacturer model      displ  year   cyl trans      drv     cty   hwy fl   
##    <chr>        <chr>      <dbl> <int> <int> <chr>      <chr> <int> <int> <chr>
##  1 audi         a4           1.8  1999     4 auto(l5)   f        18    29 p    
##  2 audi         a4           1.8  1999     4 manual(m5) f        21    29 p    
##  3 audi         a4           2    2008     4 manual(m6) f        20    31 p    
##  4 audi         a4           2    2008     4 auto(av)   f        21    30 p    
##  5 audi         a4           2.8  1999     6 auto(l5)   f        16    26 p    
##  6 audi         a4           2.8  1999     6 manual(m5) f        18    26 p    
##  7 audi         a4           3.1  2008     6 auto(av)   f        18    27 p    
##  8 audi         a4 quattro   1.8  1999     4 manual(m5) 4        18    26 p    
##  9 audi         a4 quattro   1.8  1999     4 auto(l5)   4        16    25 p    
## 10 audi         a4 quattro   2    2008     4 manual(m6) 4        20    28 p    
##    class   mpg_ratio
##    <chr>       <dbl>
##  1 compact     0.621
##  2 compact     0.724
##  3 compact     0.645
##  4 compact     0.7  
##  5 compact     0.615
##  6 compact     0.692
##  7 compact     0.667
##  8 compact     0.692
##  9 compact     0.64 
## 10 compact     0.714
## # … with 224 more rows
```
]

---

### Question #6

.reallytiny[

#### Wrangled Data

.reallytiny[

```
## # A tibble: 7 x 5
##   class      min_mpg mean_mpg median_mpg max_mpg
##   <chr>        <int>    <dbl>      <dbl>   <int>
## 1 2seater         23     24.8       25        26
## 2 compact         23     28.3       27        44
## 3 midsize         23     27.3       27        32
## 4 minivan         17     22.4       23        24
## 5 pickup          12     16.9       17        22
## 6 subcompact      20     28.1       26        44
## 7 suv             12     18.1       17.5      27
```
]

---

## Joining Demo

.pull-left[

```r
x
```

```
## # A tibble: 3 x 2
##   value xcol 
##   <dbl> <chr>
## 1     1 x1   
## 2     2 x2   
## 3     3 x3
```
]
.pull-right[

```r
y
```

```
## # A tibble: 3 x 2
##   value ycol 
##   <dbl> <chr>
## 1     1 y1   
## 2     2 y2   
## 3     4 y4
```
]

---

## `inner_join()`

.pull-left[

```r
inner_join(x, y)
```

```
## # A tibble: 2 x 3
##   value xcol  ycol 
##   <dbl> <chr> <chr>
## 1     1 x1    y1   
## 2     2 x2    y2
```
]
.pull-right[
<img src="img/05/inner-join.gif" style="display: block; margin: auto;" />
]

---

## `left_join()`

.pull-left[

```r
left_join(x, y)
```

```
## # A tibble: 3 x 3
##   value xcol  ycol 
##   <dbl> <chr> <chr>
## 1     1 x1    y1   
## 2     2 x2    y2   
## 3     3 x3    <NA>
```
]
.pull-right[
<img src="img/05/left-join.gif" style="display: block; margin: auto;" />
]

---

## `right_join()`

.pull-left[

```r
right_join(x, y)
```

```
## # A tibble: 3 x 3
##   value xcol  ycol 
##   <dbl> <chr> <chr>
## 1     1 x1    y1   
## 2     2 x2    y2   
## 3     4 <NA>  y4
```
]
.pull-right[
<img src="img/05/right-join.gif" style="display: block; margin: auto;" />
]

---

## `full_join()`

.pull-left[

```r
full_join(x, y)
```

```
## # A tibble: 4 x 3
##   value xcol  ycol 
##   <dbl> <chr> <chr>
## 1     1 x1    y1   
## 2     2 x2    y2   
## 3     3 x3    <NA> 
## 4     4 <NA>  y4
```
]
.pull-right[
<img src="img/05/full-join.gif" style="display: block; margin: auto;" />
]

---

## `semi_join()`

.pull-left[

```r
semi_join(x, y)
```

```
## # A tibble: 2 x 2
##   value xcol 
##   <dbl> <chr>
## 1     1 x1   
## 2     2 x2
```
]
.pull-right[
<img src="img/05/semi-join.gif" style="display: block; margin: auto;" />
]

---

## `anti_join()`

.pull-left[

```r
anti_join(x, y)
```

```
## # A tibble: 1 x 2
##   value xcol 
##   <dbl> <chr>
## 1     3 x3
```
]
.pull-right[
<img src="img/05/anti-join.gif" style="display: block; margin: auto;" />
]

---

## Code Style

>"Good coding style is like correct punctuation: you can manage without it, butitsuremakesthingseasiertoread."
>
>Hadley Wickham

- Style guide for this course is based on the Tidyverse style guide
  - [http://style.tidyverse.org/](http://style.tidyverse.org/)
- There's more to it than what we'll cover today. We'll mention more as we 
  introduce more functionality throughout the semester.

---

### File names and code chunk labels

- Do not use spaces in file names, use `-` or `_` to separate words.
- Use all lowercase letters.

```r
# Good
ucb-admit.csv

# Bad <- 
UCB Admit.csv
```

---

### Assignment, object creation

Use `<-`, not `=`

```r
# Good
x <- 2

# Bad
x = 2
```

In an `R` chunk, Windows users may use Alt and - together (the hyphen key) as a
shortcut. Mac users may use Option and -.

---

## Object names

- objects should be nouns (functions should be verbs)
- Use an `_` to separate words in object names.
- Use informative but short object names.
- Do not reuse object names within an analysis.
- Don't choose existing function names or names that have special meaning in
  R such as `NA`, `T`, `NaN`, `pi`, etc.

```r
# Good
acs_employed

# Bad
acs.employed
acs2
acs_subset
acs_subsetted_for_males
mean
NA
log
```

---

## Spacing

- Put a space before and after all infix operators (`=, +, -, <-`, etc.) and 
  when naming arguments in function calls.

- Always put a space after a comma, and never before 
  (just like in regular English).

```r
# Good
average <- mean(feet / 12 + inches, na.rm = TRUE)

# Bad
average<-mean(feet/12+inches,na.rm=TRUE)
```

---

## `ggplot2`

- Always end a line with `+`

- Always indent the next line (this should happen automatically)

```r
# Good
ggplot(diamonds, mapping = aes(x = price)) +
  geom_histogram()

# Bad
ggplot(diamonds,mapping=aes(x=price))+geom_histogram()
```

---

## Quotes

Use `" "`, not `' '`, for quoting text. The only exception is when the text 
already contains double quotes and no single quotes.

```r
ggplot(diamonds, mapping = aes(x = price)) +
  geom_histogram() +
  labs(title = "Shine bright like a diamond", # Good
       x = "Diamond prices",                  # Good
*      y = 'Frequency')                       # Bad
```