R studio Chapter 1

Question 1

R lab comment starts with?

Answer 1

#

Question 2

Assign value 42 to a variable X

Answer 2

x< -42

Question 3

The quotation marks” “ is to indicate…

Answer 3

the variable is of type character.

Question 4

What are Numerics, integers, logical?

Answer 4

Numerics are decimal values like 4.5. Integers are also numerics but in natural numbers. Logical is boolean values like TRUE or FALSE.

Question 5

Class()

Answer 5

It checks the type of data.

Question 6

Is.character(v)

Answer 6

It checks if a variable is a character.

Question 7

what are commands for coercion for taming the data?

Answer 7

as.logical(), as.numeric(), as.integer(), as.character()

Question 8

Create a vector.

Answer 8

c( , )

Question 9

Select the letter “a” from character_vector

character_vector (“a”, “b”, “c”)

Answer 9

character_vector [1]

Question 10

Select the second and the third element of boolean_vector 
boolean_vector c(TRUE, FALSE, FALSE)

Answer 10

boolean_vector [c(2,3)]

Question 11

for less than, 
for more than, 
for less than and equal to, 
for more than and equal to, 
equal to each other,
not equal to each other

Answer 11

<
> 
<=
>=
==
!=

Question 12

Print the items from numeric_vector that are larger than 10 
numeric_vector c(1, 10, 35)

Answer 12

numeric_vector [c(FALSE, FALSE, TRUE)]

Question 13

Construct a matrix with 5 rows and 4 columns containing the numbers 1 up to 20 and assign it to the variable m. Specify the byrow argument to be TRUE

Answer 13

matrix(1:20, byrow=TRUE, nrow=5, ncol=4)

Question 14

The term factor refers to…?
A good example of a categorical variable is?
Command for turning vector into a factor?

Answer 14

a statistical data type used to store categorical variables. Categorical variables, unlike continuous variables, have a limited range.
“student” and “not student” are two values of the categorical variable.
factor (variable)

Question 15

functions to inspect the dataframes:
What command prints the first 6 rows of the dataframe?
What command prints the last 6 rows?
What command prints the structure of your dataframe?
What command prints the dimensions, that is, the number of rows and columns of your dataframe?
What command prints the names of the columns of your dataframe?

Answer 15

head
tail
str
dim
colnames

Question 16

What is a command for constructing dataframe?

Answer 16

data.frame( , , ,)

Question 17

In the dataframe named planet_df, how would you select elements in first row, and 2nd and 3rd column?

Answer 17

planet_df [1, 2:3] or planet_df [1, c(2,3)]

Question 18

In the dataframe named planet_df, how would you select all the elements on 3rd column?

Answer 18

planet_df [ , 3 ].

Question 19

What command allows you to gather a variety of objects under one name?

Answer 19

list(item 1, item 2 ,item 3 ) They can be vectors, matrices, or data frames.

Question 20

Grab the second element of my_list.

Answer 20

my_list [ [2] ]

Question 21

Grab the first column of the third component of my_list

Answer 21

my_list [ [3] ][ , 1]