The post is about Sampling in R Language. There are 20 multiple-choice questions from the sampling, ggplot2 package, and R language basics too. Let us start with the Quiz sampling in R Language.

R Language Online Quiz with Answers

The `dplyr`

package is used for data manipulation and transformation. It gives a set of functions that make it easy to perform common data manipulation tasks, which include (1) filtering, (2) grouping, (3) summarizing, (4) arranging, and (5) joining data frames.

The package is part of the *tidyverse*, a collection of R packages designed to work together seamlessly for data analysis and visualization.

Some key functions available in d`plyr`

R Package include:

`filter()`

: Used to subset rows based on specified conditions.`select()`

: Used to choose specific columns from a data frame.`arrange()`

: Used to reorder rows based on one or more columns.`mutate()`

: Used to create new columns or modify existing ones.`group_by()`

: Used to group data by one or more variables.`summarize()`

: Used to compute summary statistics for groups of data.`join()`

: Used to merge data frames based on common keys.

The `dplyr`

package provides a powerful and efficient toolkit for data manipulation in R.

### Quiz Sampling in R Language

- What is the class of the object defined by the expression x <- c(4, “a”, TRUE)?
- Suppose, I have a vector x <- c(3, 6, 1, 19, 12, 8)and I want to set all elements of this vector that are less than 6 to be equal to zero. What R code achieves this?
- We obtain the 10000 random sample of size 6 under SRSWOR using the following population (111, 158, 122, 193, 111, 148, 112, 128, 113, 151, 185, 200, 199, 121, 115, 114) which is the R command for repeating this procedure 150 times?
- Which is the R command for selecting a sample of size 6 from the population yp <- c(111, 159, 121, 198, 120, 136, 14, 129, 17, 115, 186, 119, 121, 153, 143)
- For the following population y<- c(1,2,3,4,5), what will be the R command for finding variance?
- For the following population x<-c(1,2,3,4,5)what will be the R command for finding the mean?
- Which is the R command for selecting a sample of size 3 from the population y<- c(11, 150, 121, 192, 233, 129, 117, 186, 129, 189, 159)
- What is the R command for generating bi-variate normal distribution
- What is the R command for selecting a sample of size $n=10$ by probability proportional to size (PPS) with $N=40$?
- Which of these dplyr verbs can be used to retrieve columns of a dataset?
- Who introduced tidyverse to “share an underlying design philosophy, grammar, and data structures, of tidy data?
- A data analyst is working with a data frame called “salary_data”. They want to create a new column named “total_wages” that adds together data in the “standard_wages” and “overtime_wages” columns. What R code lets the analyst create the “total_wages” column?
- A data analyst is working with a data frame named “stores”. It has separate columns for city (“city”) and state (“state”). The analyst wants to combine the two columns into a single column named “location”, with the “city” and “state” separated by a comma. What R code lets the analyst create the location column?
- A data analyst is considering using tibbles instead of basic data frames. What are some of the limitations of tibbles?
- A data analyst is working with a data frame named cars. The analyst notices that all the column names in the data frame are capitalized. What R code lets the analyst change all the column names to lowercase?
- In ggplot2, what function do you use to map variables in your data to visual features of your plot?
- In ggplot2, which of the following concepts refers to the shape, color, and size of data points in a plot?
- Which of the following functions lets you display smaller groups, or subsets, of your data?
- A data analyst creates a scatterplot with a lot of data points. It is difficult for the analyst to distinguish the individual points on the plot because they overlap. What function could the analyst use to make the points easier to find?
- A data analyst creates a plot for visualization. The analyst wants to add a caption to the plot to help communicate important information. What function could the analyst use?