R Programming Questions and Answers – Reading Datasets – 2

This set of R Programming Inteview Questions and Answers for freshers focuses on “Reading Datasets – 2”

1. What will be the Correct R code for the following output?

foo bar
1 1 TRUE
2 2 TRUE
3 3 FALSE
4 4 FALSE

a)

> x <- data.frame(foo = 1:4, bar = c(F, T, F, F))
> x

b)

> x <- data.frame(foo = 1:6, bar = c(F, T, F, F))
> x

c)

> x <- data.frame(foo = 1:4, bar = c(T, T, F, F))
> x

d)

> x <- data.frame(foo = 14:1, bar = c(F, T, F, F))
> x

2. Point out the wrong statement?
a) is.nan() is used to test objects if they are NA
b) is.nan() is used to test for NaN
c) NA values have a class
d) NA values have a class, so there are integer NA, character NA, etc
View Answer

3. Data frames can be converted to a matrix by calling data _______
a) as.matr()
b) as.mat()
c) as.matrix()
d) as.max()
View Answer

4. What will be the output of the following R code?

> x <- data.frame(foo = 1:4, bar = c(T, T, F, F))
> ncol(x)

a) 2
b) 4
c) 7
d) 9
View Answer

5. Point out the correct statement?
a) Using factors with labels is better than using integers because factors are self-describing
b) Factors are used to represent categorical data and can be unordered or ordered
c) Factors are important in statistical modeling and are treated specially by modelling functions like lm() and glm()
d) All of the mentioned
View Answer

6. Which of the following is invalid assignment?
a)

 > x <- list("Los Angeles" = 1, Boston = 2, London = 3)

b)

 > names(x) <- c("New York", "Seattle", "Los Angeles")

c)

 > name(x) <- c("New York", "Seattle", "Los Angeles")

d)

 > names(x) <- c("New York", "Los Angeles", "Los Angeles")

7. What will be the output of the following R code?

> x <- 1:3
> names(x)

a) NULL
b) 1
c) 2
d) 4.5
View Answer

8. What will be the output of the following R code?

> m <- matrix(1:4, nrow = 2, ncol = 2)
> dimnames(m) <- list(c("a", "b"), c("c", "d"))
> m

a)

c d
a 1 3
b 2 4

b)

c d
a 1 2
b 2 3

c)

c d
a 1 3
b 4 2

d) Error
View Answer

9. Which of the following statement changes column name to h and f?
a) colnames(m) <- c(“h”, “f”)
b) columnnames(m) <- c(“h”, “f”)
c) rownames(m) <- c(“h”, “f”)
d) rownames(m) <- c(“f”, “f”)
View Answer

10. Which of the following is used for reading tabular data?
a) read.csv
b) dget
c) readLines
d) writeline
View Answer

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