Before you start, enter the following code:
data <- mtcars
Solutions are available here.
Exercise 1
Use logical operators to output only those rows of data where column mpg is between 15 and 20 (excluding 15 and 20).
Exercise 2
Use logical operators to output only those rows of data where column cyl is equal to 6 and column am is not 0.
Exercise 3
Use logical operators to output only those rows of data where column gear or carb has the value 4.
Exercise 4
Use logical operators to output only the even rows of data.
Exercise 5
Use logical operators and change every fourth element in column mpg to 0.
Exercise 6
Output only those rows of data where columns vs and am have the same value 1, solve this without using == operator.
Exercise 7
(TRUE + TRUE) * FALSE , what does this expression evaluate to and why?
Exercise 8
Output only those rows of data where at least vs or am have the value 1, solve this without using == or !=.
Exercise 9
Explain the difference between | , || , & and &&.
Exercise 10
Change all values that are 0 in the column am in data to 2.
Exercise 11
Add 2 to every element in the column vs without using numbers.
Exercise 12
Output only those rows of data where vs and am have different values, solve this without using == or !=.
the answer to question 12 is wrong. It only produces true if one argument in the xor() equates to 1, and the other to 0. It returns false for the case where one argument is 2 and another is 1, which goes against what the question is asking.
Good point. We are changing the data in previous exercises so it’s good to reload original data before solving this one. (write and run “data <- mtcars" before writing the argument)
I am not clear on Q6.
Why does that solution work?
Also, what does data[data$am, ] and data[data$am] mean?
0=FALSE
1 or above =TRUE
so
if data$am is greater then 0, its true
if data$vs is greater then 0, its true.
TRUE & TRUE results in TRUE