Basic R Programs for Beginners

Basic R Programs for Beginners - Important Points

16.		What is the output of the following R code snippet? x <- c(1, 2, 3, 4, 5) y <- c("one", "two", "three", "four", "five") z <- data.frame(x, y) library(dplyr) group_by(z, y) %>% summarize(mean_x = mean(x), sd_x = sd(x))

16.

What is the output of the following R code snippet?

x <- c(1, 2, 3, 4, 5)
y <- c("one", "two", "three", "four", "five")
z <- data.frame(x, y)
library(dplyr)
group_by(z, y) %>%
summarize(mean_x = mean(x), sd_x = sd(x))

A. A data frame with three columns: y, mean_x, and sd_x, containing the unique values of y in the z data frame, along with the mean and standard deviation of the x values for each value of y.

B. A data frame with two columns: mean_x and sd_x, containing the mean and standard deviation of the x values in the z data frame, grouped by the y values.

C. An error message, because the group_by function can only be used on numeric columns.

D. An error message, because the summarize function cannot be used on grouped data.

View Answer Discuss Work Space

Answer: option a

Explanation:

The code defines two vectors x and y, then combines them into a data frame using the data.frame function. The dplyr library is loaded with the library function. The group_by function is used to group the z data frame by the y column, and the summarize function is used to generate a summary of the grouped data, including the mean and standard deviation of the x values for each value of y. The resulting data frame has three columns: y, mean_x, and sd_x.

17.		What is the output of the following R code snippet? x <- c(1, 2, 3, 4, 5) y <- c("one", "two", "three", "four", "five") z <- data.frame(x, y) library(ggplot2) ggplot(z, aes(x = x, y = y)) + geom_point()

17.

What is the output of the following R code snippet?

x <- c(1, 2, 3, 4, 5)
y <- c("one", "two", "three", "four", "five")
z <- data.frame(x, y)
library(ggplot2)
ggplot(z, aes(x = x, y = y)) + geom_point()

A. A scatterplot with points at the (x, y) coordinates of the data in the z data frame.

B. A scatterplot with points at the (y, x) coordinates of the data in the z data frame.

C. An error message, because ggplot2 cannot be used with data frames.

D. An error message, because geom_point() cannot be used with non-numeric data.

View Answer Discuss Work Space

Answer: option a

Explanation:

The code defines two vectors x and y, then combines them into a data frame using the data.frame function. The ggplot2 library is loaded with the library function. The ggplot function is used to create a scatterplot with the x values on the x-axis and the y values on the y-axis, and the geom_point function is used to add points at the (x, y) coordinates of the data in the z data frame.

18.		What is the output of the following R code snippet? x <- c(1, 2, 3, 4, 5) y <- c("one", "two", "three", "four", "five") z <- data.frame(x, y) library(ggplot2) ggplot(z, aes(x = y, y = x)) + geom_bar(stat = "identity")

18.

What is the output of the following R code snippet?

x <- c(1, 2, 3, 4, 5)
y <- c("one", "two", "three", "four", "five")
z <- data.frame(x, y)
library(ggplot2)
ggplot(z, aes(x = y, y = x)) + geom_bar(stat = "identity")

A. A bar chart with bars at the y-axis labels "one", "two", "three", "four", and "five", with heights corresponding to the x values in the z data frame.

B. A bar chart with bars at the x-axis labels "one", "two", "three", "four", and "five", with heights corresponding to the y values in the z data frame.

C. An error message, because ggplot2 cannot be used with non-numeric data.

D. An error message, because the geom_bar function cannot be used with non-numeric data.

View Answer Discuss Work Space

Answer: option a

Explanation:

The code defines two vectors x and y, then combines them into a data frame using the data.frame function. The ggplot2 library is loaded with the library function. The ggplot function is used to create a bar chart with the y values on the x-axis and the x values on the y-axis, and the geom_bar function is used to add bars at the y-axis labels "one", "two", "three", "four", and "five", with heights corresponding to the x values in the z data frame.

19.		What is the output of the following R code snippet? x <- c(1, 2, 3, 4, 5) y <- c("one", "two", "three", "four", "five") z <- data.frame(x, y) library(ggplot2) ggplot(z, aes(x = y, y = x)) + geom_boxplot()

19.

What is the output of the following R code snippet?

x <- c(1, 2, 3, 4, 5)
y <- c("one", "two", "three", "four", "five")
z <- data.frame(x, y)
library(ggplot2)
ggplot(z, aes(x = y, y = x)) + geom_boxplot()

A. A boxplot with boxes at the y-axis labels "one", "two", "three", "four", and "five", with widths corresponding to the x values in the z data frame.

B. A boxplot with boxes at the x-axis labels "one", "two", "three", "four", and "five", with heights corresponding to the y values in the z data frame.

C. An error message, because ggplot2 cannot be used with non-numeric data.

D. An error message, because the geom_boxplot function cannot be used with non-numeric data.

View Answer Discuss Work Space

Answer: option b

Explanation:

The code defines two vectors x and y, then combines them into a data frame using the data.frame function. The ggplot2 library is loaded with the library function. The ggplot function is used to create a boxplot with the y values on the x-axis and the x values on the y-axis, and the geom_boxplot function is used to add boxes at the x-axis labels "one", "two", "three", "four", and "five", with heights corresponding to the y values in the z data frame.

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