R Programming Mock Test 4

10%

Question 1 of 10

1. Point out the correct statement?

Reordering rows of a data frame is normally easier to do in R

The dplyr package provides any “new” functionality to R

You can also omit variables using the select() function by using the negative sign

The arrange() function also allows a special syntax that allows you to specify variable names based on patterns

Question 1 of 10

Question 2 of 10

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

> x <- as.Date("2012-03-01")
> y <- as.Date("2012-02-28")
> x-y

Time difference of 3 days

Time difference of 2 days

Time difference of 5 days

Time difference of 1 days

Question 2 of 10

Question 3 of 10

3. ________ add new variables/columns or transform existing variables.

arrange

add

mutate

apped

Question 3 of 10

Question 4 of 10

4. The _________ function is used to generate summary statistics from the data frame within strata defined by a variable.

group()

groupby()

arrange

group_by()

Question 4 of 10

Question 5 of 10

5. Point out the correct statement?

Times use the POSIXct and POSIXlt class

All of the mentioned

Character strings can be coerced to Date/Time classes using the strptime function

Dates and times have special classes in R that allow for numerical and statistical calculations

Question 5 of 10

Question 6 of 10

6. Connections to text files can be created with the ________ function.

bzfile

file

url

gzfile

Question 6 of 10

Question 7 of 10

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

 
> x <- list(foo = 1:4, bar = 0.6, baz = "hello")
> name <- "foo"
> x$name

NULL

Question 7 of 10

Question 8 of 10

8. Multiple objects can be de parsed at once and read back using function _____

read()

dget()

source()

dput()

Question 8 of 10

Question 9 of 10

9. Which of the following code extracts 1st element of the 2nd element?

 > x <- list(a = list(10, 12, 14), b = c(3.14, 2.81))

x[[c(2, 1,1)]]

x[[(2, 2,1)]]

x[[c(1, 2)]]

x[[c(2, 1)]]

Question 9 of 10

Question 10 of 10

10. .RData extension used when we save data using the functions ___________

save.image()

save and save.image functions

save()

serialize()

Question 10 of 10