Functions & Methods in R

Question 1

What is the use of getwd() method ?

Answer 1

Get present working directory .

Question 2

What is the use of require() method ?

Answer 2

It is used for searching a library is installed or not .
require(packageName)

Question 3

What is the use of library() method ?

Answer 3

This method is used to include packages in R Code
library(packageName)

Question 4

What is the use of length() method ?

Answer 4

This method is used to know how many members are in list , vector , dataframe etc.

Question 5

What is the use of class() method ?

Answer 5

This method is used to know object type of variable , like integer,chars,numeric, etc.

Question 6

What is the use of typeof() method ?

Answer 6

This Method is used to know Data Structure or container of object.
typeof(variable)

Question 7

What is the use of str() method ?

Answer 7

str() method is used to know structure of Data Frame

Question 8

What is the use of is.na() method ?

Answer 8

This method is used to find Null valeus in dataFrame
IT returns TRUE or FALSE value
my_vec4 = c(1, 2, NA, 4)
is.na(my_vec4)
is.na(dataFrame$column)

Question 9

What is the use of anyNA() method,
How we use it ?

Answer 9

This method is used to know , if vector or data frame has any NA value or not
anyNA(my_vector)
anyNA(dataFrame$column)

Question 10

What is the use of c() method ?

Answer 10

This method is used to create vectors .

Question 11

What is the use of seq() method ?

Answer 11

This method is used to create vectors
my_vect= seq(from=1, to=10, by=1)

Question 12

What is the use of list() method

Answer 12

This function f is used to create list object.
my_list= list(24,’MyName’,c(‘A’,’B’,’C’))

Question 13

What are the use of names() function ?

Answer 13

names() function is used to create slots of list on column names
my_list = list(24,’Name’,c(‘A’,’B’,’C’))
names(my_list) =c(‘Col-1’,’Col-2’,’Col-3’)

Question 14

What is the use of matrix() function and what is the proper format to use the function ?

Answer 14

Matrix function is used to create matrix.
my_matrix= matrix(c(1,2,3,4,5,6,7,8,9),nrow=3,ncol=3,byrow=TRUE)

Question 15

What is the use of rownames() method ?

Answer 15

We use a rownames() method into ways,
1. Give the row names while manually creating the data frame
2. Getting or extracting role names from Data frame

rownames() method is used to create a row names in manual data frames
It also be used to get row names of data Frame

rownames(dataFrame)

Question 16

What is the use of colnames() method ?

Answer 16

colnames() method is used to create a column names in manual data frames.
It can also be used to fetch column names from dataFrame

Question 17

print() function is used for ?

Answer 17

print() function is used to display strings

Question 18

What is the use of setwd() method

Answer 18

setwd() is used to set working directory

Question 19

What is the use of head() method ?

Answer 19

head() method is used to show first n rows of data Frame
head(DataFrame,5)
It shows first five rows
head(df) By default it shows 6 rose

Question 20

What is the use of tail() method ?

Answer 20

tail() method is used to show last n rows of data Frame
tail(DataFrame,5)
It shows last five rows
tail() by default it shows only 6 rows

Question 21

How To know the total row and columns of data frame ?

Answer 21

We have to use dim() method
dim(dataFrame)

Question 22

What is the use of nrow() method ?

Answer 22

This method is used in 2 ways .
1. While creating Matrix to define rows
2. To get number a rows of data frame

It is used to get total rows in data Frame.
nrow(dataFrame)

It also used in while creating matrix to define rows & columns
mymatrix = matrix(c(1,2,3,4,5,6,7,8,9),nrow=3,ncol=3,byrow=TRUE)

Question 23

What is the use of ncol() method ?

Answer 23

This method Can be used into ways:
1. While creating matrix to define number of columns.
2.It is used to get total columns in a data Frame

Question 24

What is the use of levels() method

Answer 24

levels() method is used to show Categorised values of of factor

Question 25

What is the use of factor() method?

Answer 25

factor() method is used categorised predefined values or column values.

Question 26

What is the use of read.csv() method
And what is the correct format to use the function?

Answer 26

read.csv() method You have to create data frame from file

Question 27

What are the use of mean() method?

Answer 27

mean() method is is used to calculate average of integer column values by using mean method .

mean(dataFrame$column)

Question 28

What is the use of apply() method
What is the correct format to use this method ?

Answer 28

apply() method is used to find mean of all column values at once, mean of rows is also possiible.
apply(dataFrame,2,mean)

Question 29

What is the use of setwd() ?

Answer 29

It is used to change working rdirectory.
setwd(‘pathToDirectory’)

Question 30

What options are used in read.csv method while creating dataFrame ?

Answer 30

header , row.names , streingAsFactors

1. header = TRUE ,means treat first row as col names
2. row.names = 1 , means treat 1st column as row name
3. stringAsFactors = FALSE