ch2_exercise.Rmd

---
title: "單一變數與函數 - 隨堂練習"
author: "Yao-Jen Kuo"
date: "`r Sys.Date()`"
output: 
  html_document:
    self_contained: false
---

```{r, include=FALSE}
tutorial::go_interactive()
```

## 換算公里與英里

Tony 不知道全程馬拉松 42.195 公里換算成英里是多少？請用 R 語言的命令列當作計算機來幫助他。

```{r ex="km_mile_converter", type="sample-code"}
# 1 km equals to 0.621371192 miles
km_to_mile <- ___

# Print km_to_mile in the console


# The distance of full marathon measured in km
full_marathon_km <- 42.195

# The distance of full marathon measured in mile
full_marathon_mile <- ___
  
# Print full_marathon_mile in the console

```

```{r ex="km_mile_converter", type="solution"}
# 1 km equals to 0.621371192 miles
km_to_mile <- 0.621371192

# Print km_to_mile in the console
km_to_mile

# The distance of full marathon measured in km
full_marathon_km <- 42.195

# The distance of full marathon measured in mile
full_marathon_mile <- full_marathon_km * km_to_mile
  
# Print full_marathon_mile in the console
full_marathon_mile
```

```{r ex="km_mile_converter", type="sct"}
test_object("km_to_mile", incorrect_msg = "Assign 0.621371192 to `km_to_mile`.")
test_object("full_marathon_mile", incorrect_msg = "Calculate `full_marathon_mile` by multiplying `full_marathon_km` with `km_to_mile`.")
test_output_contains("km_to_mile", incorrect_msg = "Make sure to print `km_to_mile`.")
test_output_contains("full_marathon_mile", incorrect_msg = "Make sure to print `full_marathon_mile`.")
success_msg("Thank you so much, now Tony knows that the distance of a full marathon course is 26.2 miles!")
```

## 建立不同類型的變數

在這個練習中熟練建立基本類型的變數：

```{r ex="create_variables", type="sample-code"}
# Create a numeric variable my_num equals to 8
my_num <- ___

# Create a integer variable my_int equals to 7L
my_int <- ___

# Create a logical variable my_logi equals to TRUE
my_logi <- ___

# Create a character variable my_char equals to "Learn R the easy way!"
my_char <- ___
  
# Use function: ls() to list all the variables we just created


# Use function: class() to check the variable types respectively
class(___)
class(___)
class(___)
class(___)
```

```{r ex="create_variables", type="solution"}
# Create a numeric variable my_num equals to 8
my_num <- 8

# Create a integer variable my_int equals to 7L
my_int <- 7L

# Create a logical variable my_logi equals to TRUE
my_logi <- TRUE

# Create a character variable my_char equals to "Learn R the easy way!"
my_char <- "Learn R the easy way!"

# Use function: ls() to list all the variables we just created
ls()

# Use function: class() to check the variable types respectively
class(my_num)
class(my_int)
class(my_logi)
class(my_char)
```

```{r ex="create_variables", type="sct"}
test_object("my_num", incorrect_msg = "Assign 8 to `my_num`.")
test_object("my_int", incorrect_msg = "Assign 7L to `my_int`.")
test_object("my_logi", incorrect_msg = "Assign TRUE to `my_logi`.")
test_object("my_char", incorrect_msg = "Assign \"Learn R the easy way!\" to `my_logi`.")
test_function("ls", incorrect_msg = "Call ls() to list all the variables.")
msg <- "Have you called class() on all the variables you just created?"
test_output_contains("class(my_num)", incorrect_msg = msg)
test_output_contains("class(my_int)", incorrect_msg = msg)
test_output_contains("class(my_logi)", incorrect_msg = msg)
test_output_contains("class(my_char)", incorrect_msg = msg)
```

## 運算並觀察類型

把上一個練習所建立的變數拿來運用：

```{r ex="calculate_variables", type="pre-exercise-code"}
# Create variables from the last exercise
my_num <- 8
my_int <- 7L
my_logi <- TRUE
my_char <- "Learn R the easy way!"
```

```{r ex="calculate_variables", type="sample-code"}
# Add my_num and my_int


# Use class() to check the result above


# Add my_int and my_logi


# Use class() to check the result above


# Re-assign my_logi with FALSE


# Add my_num and my_logi


# Use class() to check the result above

```

```{r ex="calculate_variables", type="solution"}
# Add my_num and my_int
my_num + my_int

# Use class() to check the result above
class(my_num + my_int)

# Add my_int and my_logi
my_int + my_logi

# Use class() to check the result above
class(my_int + my_logi)

# Re-assign my_logi with FALSE
my_logi <- FALSE

# Add my_num and my_logi
my_num + my_logi

# Use class() to check the result above
class(my_num + my_logi)
```

```{r ex="calculate_variables", type="sct"}
test_output_contains("15", incorrect_msg = "Did you add `my_num` with `my_int`?")
test_output_contains("8L", incorrect_msg = "Did you add `my_int` with `my_logi`?")
test_student_typed("my_logi <- FALSE", not_typed_msg = "Did you re-assign FALSE to `my_logi`?")
test_output_contains("8", incorrect_msg = "Did you add `my_num` with `my_logi`?")
msg <- "Did you call class() to check the result?"
test_output_contains("class(my_num + my_int)", incorrect_msg = msg)
test_output_contains("class(my_int + my_logi)", incorrect_msg = msg)
test_output_contains("class(my_num + my_logi)", incorrect_msg = msg)
success_msg("Well done!")
```